Atheon is just great when it works. You can Horn him within 20 seconds, but you can also beat him legit without dying. Do a clean portal run, take good positions and aim while one keeps the supplicants in check. There is a proper strategy that lets you beat him with blue weapons even. Oracle disruptor was a useful perk, and near required on HM.
Crota was good on paper, but 5 players simply hammering a shield and one having to melee him didn't work out well imho. Oversoul perk was fucking useless and hive disruptor fucks Black Hammer. Its not well thought out at all.
Skolas without horn overkill and no solar burn, good luck. Its a badly designed fight, another one.