Player since release here. Got a bit of salt but will try to refrain from spreading it in my post.
Suggestion: Try to beat Dark Omens on legend w/o a cheesy comp like ironbreaker w/ shield, merc kruber, unchained sienna, and zealot. Get a feel for what the beastmen are really like compared to other factions, and how poorly designed certain sections/encounters are in Dark Omens
What you will be sure to find:
There are too many sections where waterfalls are inevitable. The leadup to the finale is basically a giant waterfall trap with beastmen dropping in left and right. Makes for a very VERY tough encounter, especially since banners can be placed above you
Beastmen are tough. Very tough. Very hard hitting. Very fast, and silent. A lot of things you don’t want in a basic horde. I can tell you with confidence that I fear beastmen hordes with a single banner more than a boss spawn + a skaven horde + specials.
HOLY SIGMAR the finale is insanely hard. For one the area is completely open meaning you WILL get surrounded and backstabbed. Second, a minotaur spawns (in legend) meaning you not only have to deal with 50+ beastmen, but a tanky, hyperaggressive boss as well. Lastly, the interaction between banners and beastmen means if you do get surrounded near a banner (very likely) you will almost certainly get downed.
I’ve actually faced legendary deeds that were easier than this map. Try vanguard + harder better faster stronger Athel Yenlui. It’s not nearly as bad as Dark Omens on legend.