I don't know if it's a known bug or not, but it's game-breaking so I thought I'd report it. In trials Elemental Drain seems to restora magicka only to the player who applied it, not to anyone else (or maybe very very rarely). Many different people tried to apply it, yet the results were the same, it'd restore magicka only to the one person who applied it. It seems to work on training skeletons (so when applied to target skeletons it restores magicka to everyone), but for some reason not in trials.
Immortal Redeemer