That would be interesting actually, might be doable with enough mastery.
However, I've been trying some 25 hcs of cata, did magmaw, omnotron and atramedes in BWD, magmaw requiring a bit more mastery and tank meta (for me, that is), omnotron being doable in full dps, and atramedes requiring more attempts than the others, buffs and enough stamina to outheal the wiping ability he uses at 100 sound for all the fight while still having enough dps gear to get him at 6 mil when he enraged, so I could finish him with all cds.
In FL so far I did alysrazor and shannox 25 hc, alysrazor back with 564 item level dps gear, shannox 577 or so 170% mastery and used the trick to kill riplimb to reset stacks, once was enough.
And then I tried bot 25 hc, as 2nd and 3rd bosses are doable and shouldn't be complete nightmares like, for example, the first boss due to healing reduction drake.
Gave valiona and theralion a few tries, but they have 164 mil hp compared to about 78 mil on 25 normal, the difference is huge! Also due to the mechanic that sends me inside the twilight realm and I keep getting more stacks, and the adds inside that keep spawning I just cannot outheal all of that in dps gear.
It's also magic damage, so mastery doesn't help either, even with a 1,15 mil hp stamina set I was only able to survive 9 min 30 and get bosses to 65 mil hp or so, there's only 1 video of youtube (quicktum did it) and he has 1,2 mil hp, 4x tank set bonus and quite high mastery, from armory he has bis tank gear (the one time I saw him wearing it) and he outhealed enrage from 40 mil to 0.
The problem is I don't think I'm too undergeared for the fight (578 dps gear and 577 with a 100% mastery and 1,15 mil hp stamina set and again, only magic damage is the issue till before enrage), even on atramedes he enraged at 19% initially, then with some more crit gear I managed to make him enrage at 6% and kill him, but on this fight I just can't handle all the adds quickly enough to not get insane amounts of shadow damage debuff (100 stacks is cap but it hurts).
For now, I gave up, killed them on 25 normal in dps gear in 5 min 30 and did elementium monstrosity 25 hc, what was fun in the end (did it in full dps gear 78% mastery, once again, only magic damage mattered), had 150k left, but I plan to go back to theralion and valiona next week, so would like to know if anyone tried\did it and has any ideas to improve.
For one, on my last try, I managed to do 78 millions damage in about 7 mins (when I died) by trying to max dps (drw when I could and ignored adds in those seconds) when theralion's 100% damage and healing buff was active, but it would only mean 114 millions at the enrage, so enraged at 50 mil is still 10 mil slower than the video, so survival and enrage issues at the same time!