Accessories for WHM suck. We are not a Crit Build..yes crit heals are nice. Love when I can crit for 3500hp its wonderful...but we're not a crit build.

Spend your Myth Tomes are your other gear. Pants, Boots, gloves. Depends on how far into Coil you're getting. I recommend doing at least ring and maybe wrist with Astral. Cap it for HP, that'll give you the boost you need for later turns. If you don't have at least 4000+ unbuffed healing T5 is going to be brutal.

I have Vanya Hat because I haven't had any luck with allagan.

Det or SS? Different schools of thought. I don't personally know if one is actually better than the other. BUT what i do know for sure is one item with SS isn't going to help. You either need to stack it or nothing. Determination will give you bigger heals, by a little but can make a difference stacked. SS can make you heal faster, not as much but faster, if stacked.

Pick for play style. You a clutch healer or a big BAM healer.