don't forget: if they use UltraNova first turn, they don't activate their drone. So they are trading some overall damage (esperally if all their weapons except drone are one-use or two-use) in exchange for tactical advantage (ability to attack and not be attacked). Sometimes this exchange is helpful, sometimes is not.
Either way, if your mech is resilent enough, you shouldn't be hurt that much, and you activate drone first turn and deal more total damage. In case with limited-use weapons mech, if he unloads everything he got on you and you still live, you obviosly won.
one last thing: don't forget that lower-rank (and thus weaker) mech is awarded first turn in battle