It's a good power, but it works well out of the box and doesn't require a lot of slots. The only enhanceable aspect of the power that affects survivability is the tohit debuff. It has a 1 second duration, so it only affects mobs that stay within the power's radius. It doesn't protect you against ranged attacks. The debuff is 5.625% base, 6.75% with 1 SO, 7.7875% with 2 and 8.775% at ED max, so if you want to devote the slots to it, you pick up about 1% additional debuff for each additional slot. I don' think any of the tohit debuff IO sets give you exciting bonuses at the 3-slot level, so I don't see a lot of value in going that route.