In fact the idea of "focus down the big targets" is a call generally made on the move and/or on enemies on the move, as you; A; minimise the chance of having friendlies miss the target. B; Minimise their extra armor rates by focusing as a group. And C; They are the last targets you want to ignore and risk getting behind your lines.
Otherwise in most cases targets are just called when they are spotted, size doesn't really come into account in that first reaction.
In QP it all mostly tends to come apart, but you can still see it apply at times. The major issues there come in the disparity of styles and skill, and lack of communication. The old assault yelling "I pushed in where was my team" after the fact instead of letting anyone know as he was going to push in (or not realising he had 11 hill peepers). Or the old "I see an assault looking like he is about to push, go to push with him, and realise he was just peeping and is already back in cover when you get shot", instead of asking him what his intent was etc..
Also that extra total armor as an assault means F all to someone who refuses to twist, or just lets their back get cored out etc. The reasons lighter mechs survive at comparable rates is because they tend to at least move if not twist (or both), any kind of movement against most types of fire will save your bacon immensely, it seems like in bigger mechs people often just throw those tanking tactics out the window, assuming their extra armor will just magically save them from being cored out as they stare down targets.
Edited by Shifty McSwift, 14 November 2017 - 07:42 PM.