Warlock Trinket Question

I've been playing around with different trinkets for a while now and I can't make up my mind which are best for different circumstances. I always use my heroic DSI but other than that it gets kind of hazy especially for destro.

I have a heroic DSI, a heroic class trinket, a mythic Piston, a Sandman's pouch, the demon trinket, and a 725 (after upgrades) Fleshrender's Meathook. No GSR or Darmak trinket, and won't be able to get one unless I find a PuG.

For affliction I've been using the class trinket for most non demon fights, and using the meathook for fast kills on Reaver and Kormrok, and then the demon trinket for Fel Lord.

For Destro I've been using the Piston on Assault, somtimes on Killrog, Soc, and Xhul. The demon trinket for Gorefiend and Archi. And the class trinket on Iskar, and sometimes Kilrog.

I feel like I have a pretty good handle on the uses but I'm not sure if the Sandman's pouch beats out the piston, and if so on what fights. Any other trinket advice is also nice as well since I'd like to get a handle on trinkets before my guild starts to push into Mythic more regularly.