The way I understand it, there are Scout - a light mech whose purpose is information gathering. Useful for abusing sensor lock if you have 3 LRM boats, but otherwise useless. Skirmisher - a light mech or medium mech whose primary purpose is to deal tons of damage while avoiding taking hits themselves. Best used by reserving a lighter Mech until everything else has gone, sneaking in to get a few hits and getting away. Bonus if you are an Ace Pilot and can shoot twice and move without exposing yourself. Brawler - a heavy Mech with tons of armor and short-range weapons, designed to be on the front line and draw the enemy's fire. Assaults with one or two long range weapons, and everything else short range, are still brawlers. Jack - a Jack-of-all-Trades has enough armor and short range firepower to tank, and enough ranged firepower to at least do something from ranged. Fire Support - While LRM boats technically could fall into this category, fire support is a Mech whose primary weapons exist from long range: PPCs, LLs, AC2s and AC5s, and Gauss. A mech may have these in tandem with LRMs. LRM Boat - A Mech dedicated to LRMing To go over them in a bit more detail: Scout Information is a very valuable tool, but beyond knowing where the enemy is initially coming from, a scout doesn't seem to do much. A skirmisher can do the same job almost as well - if not just as well - and can serve the same role as a scout. What I mean by this is, a scout is usually a fast light mech, such as a Spider or a Locust. These things are incredibly squishy and have no firepower. A skirmisher is going to be something like a Firestarter, Jenner, or maybe a medium mech like a Cicada or a Kintaro. The problem with a scout is that once you know where the enemy is, the scout can largely be rendered useless, and it feels like you only have 3 Mechs. If the scout's limited firepower isn't enough, the limited armor might be the deciding factor. Priorities: Mobility Skirmisher As mentioned above, the Skirmisher is a fast Mech, much lighter than everything else you bring, which uses mobility and high firepower to deliver it's payload before running away. Reserving one round to go in and deal damage, only to use your high initiative on the next round to run away is key. Master Tactician can help you get away sooner, and Ace Pilot can let you escape after firing a second salvo. A skirmisher requires skill and strategy to use well. It is far simpler to just use something on the heavier end of the spectrum instead of a skirmisher. If you don't play it right, your low armor can come back to bite you. A well-played Firestarter can easily unload 2 alphas of 170 damage each into the back of anything else without ever taking damage. A poorly played Firestarter will pop faster than a balloon in a trash compacter. Priorities: Mobility, high alpha damage Brawler Your brawler is most likely going to be your heaviest Mech, but that's not always the case. In general, it's a Mech with quite a bit of armor and a focus on being up close to the enemy. Quite often I find my brawlers end up sprinting to stay in the front of the lance, but that's okay because when they get up close, they burn hot with tons of medium lasers, small lasers, and heavy ballistics and SRMs. Sometimes you equip a brawler with a single standoff weapon, maybe a longer range ballistic or an LRM. That doesn't really make it a Jack, as that weapon isn't really used as a primary weapon, but to use while moving into brawling range. It's a joke in MWO to have a single LRM launcher on a Mech, but it makes perfect sense in BattleTech. Some brawlers also make good skirmishers. I have a Kintaro with near-max armor, 5x SRM4, and 4 jump jets. This thing is tanky enough, but also good at jumping out from behind cover and wrecking enemy Mechs with a huge salvo of 20 SRMs. Brawlers are absolutely necessary. I'd argue that unless you simply have enough weight to throw around, or you are using the LRM/scout combination, a brawler is absolutely necessary for any lance. Priorities: Armor, Short-Range Firepower, Mobility Jack The Jack-of-all-Trades is capable of doing anything, but not perfectly well. They have enough armor to be on the front line, enough mobility to be on the front line (or not), and enough firepower at any range to contribute to the fight. Early on, your brawlers will probably actually be Jacks (for example, my Shadow Hawk with SRM10, ML, and AC5...and my fastest and most armored Mech in the early game) is a Jack of all Trades, but it fills the brawler role. Unless you're in the early game or you've got really big Mechs to throw around, I wouldn't recommend using one of these guys as your primary brawler, but they can be useful for sealing off your flanks or for providing relief when your main brawler is in trouble. Of course, another brawler can do that too. Priorities: To have no priorities Fire Support Fire Support could be a sniper (especially with Gauss and PPCs) or it could be a dakka boat (with AC2s and AC5s). A fire support mech with armor and close-range weapons can fill on the front lines, but typically when you design a fire support you will sacrifice armor to increase cooling or firepower, and you want this guy to hang back. While AC2s and AC5s are nice for starting off, what you really want on this guy are PPCs, Gauss, and maybe AC10s or LRMs. The reason you would rather have a single hard-hitting weapon like a PPC over smaller weapons like an AC2 is to get bigger hits on a single component. If you can get 2 PPCs back-to-back on a single component you can often do quite a bit of damage. Priorities: Ranged damage potential LRM Boat The LRM boat is really simple to explain. It's a Mech that focuses on the use of LRMs. In the early game, the CN9-A that you get is absolutely perfect for this role. A LRM boat will do tons of stability damage, as well as being way too good of a sniper with high tactics rating. Not to mention, it doesn't have to do a good job of getting in line of sight to the enemy. Priorities: LRMs Lance Building To build your Lance, there are 2 ways you can approach it. Option 1 is to simply use a scout and 3 LRM boats. This is a simple tactic of using sensor lock with the scout, and then using the LRMs for their indirect fire potential. However, aside from that cheap group combination, this is what I recommend: Your first mech is a brawler. This guy is going to stay up front in the formation as you move up, and his job is to soak hits more than it is to give them. This guy may not be that fast, but he will double as your scout, as you often want him to be the one to first make contact with the enemy. A Jack might work in this slot, but in general you want to focus on a brawler in this role. While bulwark might seem to be the staple ability of the brawler, and guts itself an important tree, I find piloting just as useful. Evasive Movement is nice for shrugging off hits on the way in, and the extra sprint range is nice for closing the gap to short range. Your second mech is either a brawler or a jack. This Mech is your second tank or your off-tank ("tank" being the RPG term of a unit designed more to take damage than to give it). When you have multiple fronts, the #2 Mech should be sealing the second front so the enemy can't get to you, which means it must have the armor to deal with any situation. This Mech must also take over for the #1 Brawler in situations where the #1 has taken too much damage and can't stay on the front line. This Mech must be a bit more mobile than your first brawler, and sometimes might be the first one in. Your third Mech should be focused on dealing damage, either as a skirmisher, a fire support, or a jack. There's a reason I don't have this one slotted as an LRM boat. The third Mech shouldn't be on the front line, but it should be in the back of the minds of the enemy for you to deal with. This Mech uses the armor of the front-line Mechs as a shield, while it powers through the enemy with lots of firepower. Your fourth Mech should be another damage dealer, but a bit more focused. This most likely should be a LRM Boat, but a Fire Support will work pretty well. If your third was a Jack, then you may want a Skirmisher, but that's less likely to be the case. The #4 being a LRM boat will give you quite a bit of damage potential. Using this template as a guide, here is my current lance setup that's worked well for several missions: Jagermech Brawler (I know, I know): AC10, 4xML, 4xSL. This thing decimates in close range, and the 4xSL do wonders when I melee to reduce heat. Dragon Jack: AC5, SRM6, 2xML. This thing has speed, the AC5 does some ranged damage, and then it has good up close punch. Black Knight Fire Support: 2x PPC, 2x ML, 3x SL. This is my heaviest Mech, but with its focus on energy weapons I decided to put this into the Fire Support role instead. The PPCs give it a large punch and some stability damage, and the other weapons are mostly used as a backup. Centurion LRM Boat: LRM20, 2xLRM5, 2xML. I was using 2xLRM15 instead of the LRM20 and LRM5s, but decided to switch it up to make better use of Breaching Shot. I have yet to get a better LRM Mech. I think I will need to get a 65 tonner or bigger to get something that can do what my Centurion can do. I'm looking forward to getting a thunderbolt or catapult.