if you are two ppl there (like on your picture), then just get on the second "floor" (not on top) of his little temple on the left side of the stairs as a healer and the raptor will evade because of your healing aggro. your tank just stays somewhere at the beginning of the staris where he can fight mandokir and is in your line-of-sight.
nothing new and much much easier than your positioning-thingy from my point of view. maybe you should give it a try
edit: AND u can't be charged/fear/whatever by mandokir.