I've got Desecrated Shadowmoon Insignia as #1 trinket, but i can't decide between Sandman's Pouch (6/6) or Intuition Gift (heroic), can't find any IG sims for balance
That's because Intuition's Gift is a healer trinket. (see all that spirit on it)
Definitely just use sandman's 6/6 along with your DSI if you don't have the class trinket yet.
Only Mythic 2/2 IG is better than 6/6 2/2 Sandman's. Even then, you really only want to be using them on like...Iron Reaver, Kormrok, maybe Zakuun if you have very fast kills.
Why would Sandman's be better for 'very fast kills'? It's less crit and less intellect, while the buff still fits into the ring duration. If the boss is dying to ring or very shortly after it seems IG should be better.
Heirloom is obviously pretty damn good on Zakuun.
Checking Zakuun parses, there's actually someone using IG + Heirloom, which is somewhat interesting to me.