I agree with the other posts.
However I run at least 1 flail even in my dakka squads as it's fantastic output wise and has given me the edge in a lot cheap troop vs. troop battles that tend to take forever otherwise.
Got a little worse with AoC but they work still perfect against many targets.
Sure that's a lot of points if you play
PM heavy and will not always come to play but it's a nice backup plan to have.
I had 2 flails with full buffs who deleted a squad of 20 Necron warriors with the excess damage strat all by themselves.