it might not be possible to crit the bosses, but it is possible to stun them and take away their morale with the right heroes. it's about learning what does work in a game, not complaining about what doesn't. I guarantee that I do better with two stunning heroes and one who does will breaker than anyone would just getting the occasional crit. The top people in our realm spent a ton of money to have over 2 million to 3 million power each versus my 900k, and yet my little non-casher self who happened to luck into the right combo of heroes is always right there in the top three, usually fighting them for first and second place in damage.
Stop complaining about what doesn't work, and go figure out what does for you, and you'll be much better off.