It's not complicated people!!! -_-
Veteran Hard Mode Drodda only has a few notable moves:
• Light Attack: Drodda will fire light attacks from her staff at whoever she is aggroed to.
• Teleport: Drodda will teleport to a random player's location, and charge up an AoE explosion of Ice which can one-shot most players. If you see her teleport, simply move away from her. (easy to avoid)
• Summon Ice Wraith: Drodda will summon two Ice Wraiths to support her. They are not that dangerous. Best to save Ults for them though if you feel they are.
• Summon Frost Atronach: This move will replace Drodda's Summon Ice Wraith ability when she reaches 50% health. She will summon two Frost Atronachs to support her. They are only slightly more dangerous than the Ice Wraiths.
• Lifedrain: Drodda will CC a player and drain their health, signaled by a light blue beam as well as causing the affected player to levitate. It also heals her for every half second it is not broken. CC break as soon as possible to avoid letting her regenerate a ton of health!. It is highly recommended to save your Stamina so you can make sure you have enough to CC Break when needed. As a comparison, it is no different from the Drain Essence skill in the Vampire tree.
All you have to do is walk out of the big red circles, deal damage to Drodda and her adds, and save enough Stamina to break the occasional CC. It is much easier than everyone thinks.
Hope this helps!
Tried this last night with two friends I run trials with (tank and DPS), a low-cp guild mate (DPS) and me healing; first time in vet Direfrost for all of us. More or less blasted through everything in the dungeon with no issue whatsoever until Drodda.
We initially tried on hard mode and, like the OP, could not get her past 95% or so. From what I could tell everyone was breaking free of her tether very quickly but she would heal to full almost instantly. After playing the 95%-100% game for awhile we called for a wipe and tried it without reading the scroll: had no real issues there.
Hard mode certainly seemed like it was bugged, I've been running through the various new vet I dungeons with these same folks and nothing else has come close to this fight. I'm sure it's possible with a really well-structured and experienced group and I have guild-mates that have completed it, but it certainly appears over-tuned verses the other hard mode bosses.