Upon dying guard hobart's body disappears instantly and he respawns in about 5 minutes in case you were wondering, granting no XP. The same is true for the other guards but they've been blessed with higher regen, which makes killing them about 3 or 4x longer and requires better weapons to make a dent. He has moderate regen which allows a twinked noob to kill him over the course of 30-50 minutes or so. When I've done it he died after about 18k damage, however so much of that is regen that his true HP is probably closer to 8-10k a ~100 point hit takes him down 1%.
His regen is roughly 13 hp a tick. Unless your character does 3 dps or higher he'll never die.
... I was bored.