For ranged damage there are 2 non-purple sets that have recharge bonuses, entropic chaos and decimation. Both give 6.25% for 5 slots, but decimation has better enhancement values due to having six IOs in the set compared to entropic's five, one of which is a chance for self heal proc.
With the only bonuses available in ranged damage sets being 6.25% (if you're not using purples), and many of the other potential sets you can slot in Mind's powers like Call of the Sandman, Glimpse of the Abyss and Malaise's Illusion also giving 6.25% you'll probably hit your maximum of 5 of these bonuses quickly though.
There is a KNOCKBACK set that gives 7.5% Recharge with 6 slotting. You lose damage slotting, but end up with the cheapest perma-Dom available.
With Sleep and Confuse sets also very cheap, the only expensive set that you need is Basilisk's Gaze, and I think that may even be skippable since you might max out the 7.5s with the Knockback sets, depending on how many attacks you slot for max knockback.
So you get 5x7.5 from the Energy side (one could be the snipe which also has a 7.5 set in the Snipes rather than the Knockback sets), 5x6.25 from Sleep, Fear, 2xConfuse and one expensive set (either the Pet Recharge in the Patron Pet, Decimation or Entropy in a Ranged Attack, or Positron's in a Ranged AoE).
Whirling Hands gets Obliteration for the 5% recharge. You could go with Stupefy for the Stun, but it's a damage power and unlike the Knockback sets, Stupefy has no damage enhancing.
If you find that you have more than enough Recharge, you drop some Knockback sets out of melee attacks for Crushing Impacts. Bonesmasher needs CI anyhow as it doesn't take Knockback.
I decided to make a petless dom and was wondering how to make this build perma. I know some powers are easier to slot for recharge then others but what's a good IO set for ranged damage that increases(decreases?) recharge?