Right now Ubber Abby and High level Omen windows are impossible for some build styles. Not power levels, Styles.
For instance my VERY powerful zoo minion build cannot do Ubber Abby because one shot ground effects wipe out little minions even with lots of defensive investment. I cannot resummon 20+ minions in a hard fight.
Omen windows require my necro to stay in a circle, when his build style is to stay well back and let the minion doe the damage. He should be no where near monsters but the rules of the window destroy his entire build rational.
I understand you cannot make a challenge that balances all possible build styles but how about some challenges that say a zoo build could do but make it hard on some other kind of build style?