For me:
Racials - 20 Warlock, plenty capable for r1-4 leveling and with a decent gear set does fine at cap for r6-8 reaper saga Zerging. It’s kind of a lazy man’s sorc, less damage but more forgiving (more durable, less reliant on Spell points).
Random heroic classes - Horc THF 6Barb/6Ftr/8xx, super zergy (barb speed, sprint boost on rage, regular sprint boost), does tons of AoE damage (THF and great cleave by level 4), impossible to die between blood tribute then blood strength. Not great at cap, so if I do an epic life I don’t stick around, just eTR/TR immediately.