I've not tried it to know its doable, but I think with a good set of cleric buffs (including a symbol) on top of HP/stamina geared he's probably in the driving seat to do some tanking in the absence of an enchanter as the lifetaps are ample!
Rooting of course works just as well as offtanking, lets not ignore that... my cleric would regularly stun a 2nd mob and move it away from the action to root it if there was no enchanter present (worked especially well in KC and camps with a bit of space to move). Be the best you can be whatever you play
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Screaming Terror is a great pull spell to split a camp... just be sure to be FD before it wears off (with the pet tanking the mob(s) that came along) or that mob will add as well.