I play a lot of controllers and defenders, and for whatever reason, they tend to be defense-based and recharge-starved.
Genie of the Ring has Scorpion Shield 5-slotted, with 4 LotGs and the Shield Wall unique.
In addition to the +7.5% recharge, that grants:
+21.33%% strength to smashing defense on self unresistable
+21.33%% strength to lethal defense on self unresistable
17.50%% resistance to toxic damage on self unresistable
+14.22%% strength to energy defense on self unresistable
Plus the set bonuses: +5% Resist (All) from SW, +10% Regen, +1.13% HP, and the +9% Accuracy for all powers.
Which doesn't suck. The only other Mace power sans Mace is Focussed Accuracy, which I've never seen the utility of.
So: Niche, but very helpful on the right toon.