Elite Harry has 330k HP (part 5, 220k in part 4).
Elite Horoth has 350k HP.
Elite Suulo has 350k HP (in both raids).
Epic Velah has 350k HP and heals ~250hp/sec.
Never tested Epic Cojoined Abashai Devastator, but suspect it has ~250-400k HP and heals 1kHP/sec if its regen is not suppressed.
Never tested Epic Turigulon, but suspect he has ~150k HP - more than any other 6-player epic quest boss.

Normal Amrath trash has ~600-1200HP when single-player dungeon scaling is in effect.

Most Epic trash has <4k HP if it is a humanoid (some 'bigger' monsters like Fire Giants or Orthons have ~10000)