Imo, the 50% divine is way overkill, and not unique either because it mimics the Mandate. Such high exo DR should also be limited, and the cumbersome 0 ac Ely plate is a good example of balance.
Fwiw I (like any sane rich robed cleric) wear a (usually slot-auged) Warp of Raphael so you could compare that to a 6 slots +3/6 more from augmentor (maxed out it ends like mine 888999999999), but your 777888999 is quite good already for a set compared to base BUR 888999 or to 444555666778899 from the Pristine's Way from Malad. The former provides +1 dc to 1-6, and a spell immunity to 1-4 that could luckly randomize to 1-6 but, while powerful on robed cleric/druid, is useless on theurge due to EV. The latter has no added power but 5% divine and positive and some gate-backup DR.
+1 SP on all spells is vastly superior to +1 dc to 1-6 ones, if you're aiming for a 55-60 set loot then I'd say remove the 50% divine imm and the item is already very usable, as a offensive alternative to the Maladomini's robes.
For a paragon tier loot, you might look into upgrading the Devotion of Mystra from Thanatos, that was a 'ok' item before the Wraps of Raphael were introduced (and randomized to godlike levels). Add +1 SP to those, cover the missing 20/ positive resistance, add some cosmetic/cool/useful in Limbo stuff like 15/ psionic and force DR.
You know, it looks dangerously similar to the 100% outdated/useless/never been worn Ely cleric robe already, thinking about it, this item could just get a +1 sp on cleric spells and fit the same role/power level without being obsolete nor creating new stuff
What item is currently available in that slot, and does it increase SP? Not keen on adding that without some idea of the effect.
It is basically a robe alternative to Divine Chorus , to even the playing ground between robed and plated clerics. I think Divine Chorus is better; but this would be fine for 55-60 areas. Divine Chorus is one of the items that is too strong (or sufficiently strong? it can combat randomize and augmenters) - that is balanced by it's infuriating rarity.
Baneknights would be balanced if they could splash paladin. -Caeha Everyone should stop using the same portrait so I can GR them better, damnit. -Caeha