I played Chaos Gate and in that I had a strategy of leveling up the worst troops as tactical marines, my best leaders as sgts, my best shooters as heavy weapons and the worst shots as tactical bolter marines... my better ones (bar the Sgt/Heavy) were in reserve, so even if I lost the bolter marines, I had better replacements. Once I got access to Terminators, I did the same format, Best Sgt with Crux got the Squad Sgt role, then the best shot Terminator got the Assault Cannon, and the worst shots were Storm Bolters... again my better ones (bar the Sgt/Heavy) were in reserve, so even if I lost them, I had better replacements.

So I follow a similar strategy with this in keeping everyone leveled up. Although for the last couple of missions I went all out to get to the Terminator Crux... then found out that only gives access to Terminator Armour that you have found, not to an armory with it (which fluff wise is a bit dubious, given that the TA is treated like holy relics, much like the holy hand grenade of Antioch).

I treat my Tactical Marines as my command squad and all rounders. They are also my tanks so they have gone all out endurance at present. They are a mainstay and go on every mission. I swap out all the rest and have found that of the rest the Devastators are very much my next all rounders in that they do a lot of damage to everyone once they are setup (Tactical using taunt, and Scout using suppression often give the time needed for this to occur). I didn't think much of my scouts until I saw how effect the sniper rifles were against tyranid big 'uns... the special shot from that kills a Carnifex in one shot. I like Assault Marines and they are fantastic against shooty Eldar, but as I have focused purely on Melee, they don't quite have the energy to hit and run... and I don't yet have the micromanagement skills for them.

I don't get much time to play. The home PC runs the game wonderfully well... but it is my wife's work PC first and foremost. So I have only got to level 6 so far. Really want to see how flamers work.