Well, in hardmode there's 2 minibosses with 7 or 8 million health. You need to kill both of them quickly, or they will enrage and wreck everyone. You have 3 minutes to do so, and they will respawn again shortly after you kill them. Those minibosses keep teleporting so they must be positioned properly on the main boss. They still have their mechanics (so the green boss will shoot poison blast and the red one will jump on players) which makes things difficult when you have to deal with multiple mechanics at once.
Then you have spheres... Not sure how much hp they have. They shield the main boss (so he's immune to all damage while its active) and I think if you get more than one then minibosses would be shielded as well.
And of course the main boss (Olms) will do all his mechanics which means that sometimes you'll have to kite lightning sparks, kill spheres etc.
I think its doable if you do 25k dps during this fight, but if you mean 25k on a dummy that might be not enough to prevent minibosses from enraging. If its the first time for everyone in your group, you might want to practice +1 versions of the trial first so you can see the potential issues.
Anyway, even though magicka warden suffers from many issues, I'm pretty sure its possible to boost its dps to 35k+ range.

Arbit wrote: »

Is it possible to beat vAS HM say with a 25k+ group?... I am a lowly magwarden dps who can only achieve about that much and I'm sure there are others who would want to beat it, and I wondered if you knew all the mechanics would it be possible to beat it with such a group...

Short answer is yes, the fight is absolutely not a DPS race, it is very mechanic focussed and if you did 25k DPS with minimal deaths you could fairly easily kill the boss. My group cleared on Sunday and most our DPS was in the 20-30k fight during the actual fight which includes shielding, dying and ressing. The fight was just over 30 minutes and we barely ever actually focussed olms, the main boss. We would mainly be focussing the mini bosses, 2 sorcs on llothis with interrupts and the rest on felms burning him down while he was stacked and not jumping. So technically as long as you have enough DPS to kill llothis and felms before they enrage then you have enough dps to clear but as you will eventually get olms down from cleave.

That said at a point it becomes unfeasible and the fight becomes longer and longer. And also it will be very difficult to find a spot for your mag warden DPS as their overall damage is weak and they don't offer anything for the group..