As long as you don't fight on talent tiers (4/7/10/13/16/20) you can really pick a fight rather easily as long as you get good positioning to open the fight. Even some talent tiers are more important than others. Most notable 10, 16 and 20 each generally convey a rather large power spike. But some heroes get spikes elsewhere. But if you're so far behind that you're down almost two tiers the game properly punishes you completely messing up at some point in time.