I think this is quite a common tactic, but most just put the other heros into sneaking an place them ambush like in advance. It kind of make 'ambushs' pretty pointless or help to devastate half of the enemie team before the fight really started. It's kind of an abuse of the real-time outside and turn-based in fight stuff.

With sneaking, hight advantage(, guerilla) and snipe you probably can even kill them off without getting into fight, if you are far enough and manage to onehit the target.