To be honest with you vs 3 or 4 good DPS.... i wanna see one HPS who can survive one minute against them.
Maybe the merc is capable of that.
With an Tank or another DPS with you, it isnt that hard.
I actually can hit my 20k hps in Arenas and even in 25 min Novare Coast games.
HPS just feel a bit weird because u cant use ur full mobility potential, because u need to use ur gcd's more efficient than ever.