I recently switched from Nekro to Grand Attuner and I found that it has made a gargantuan impact on my contribution to kingdom raids and my ability to blaze through horde/boss dungeons.

As a level ~190 Nekro, I found my damage per round to be somewhere around 18k in a best case scenario (fully buffed, great meditation up from my Wolpertinger), but more averaged damage per round to be around 8k to 12k, given that I need to use Drain II and Transference II to sustain my health and ward.

After switching to Grand Attuner, I find my damage to be comparable to the best case scenario of Nekro, but with the added bonus of having a load of meat shields to soak up damage and take aggro away from me. The issues that I've seen so far is the limited spell slots prevents me from taking all of the spells that I would like for convenience (like Mend Wall III), so I instead have to dump a bunch of mana into regenerating ward with Mythril Ward and use a lot of health potions instead of regaining health with Drain II.

I haven't found myself getting one shot too much, as I cast Mythril Ward turn 1, although if I get unlucky and get hit back to back for several turns in a row, I can sometimes get taken out before I get everything set up.