I've really never had him come close to one-hit killing me. Even on hardcore Elite. I think you're most likely gearing wrong. On hardcore your gear needs to be focused on survivability, not offense.

Err, you need to change gear if Grell is one-hit killing you. I've killed him at level 13 with ease on every playthrough. That or you're playing online and there's 6 people fighting him or something.

Looking for a group of people interested in giving a HCE Ironman run a try.

Specificially: No rerolling, or farming. Clear everything once.

No using the shared stash.
No using any shops (this includes buying potions with your pet).
You may use enchanters you meet in the wild (but not town enchanters).

I'm aware it's a challenging way to play, that's the purpose, to challenge yourself and see how far you can make it.

Suggestions: I won't tell anyone what class they have to play by any means, but I'd recommend the class makeup of the group being fairly engineer-heavy. Forcefield is godly, not only that but it stacks (ie. two engineers both using forcefield results in everyone getting affected by both forcefields). That and healing bot helps with the "No buying potions" rule.