As mentioned above, Naglfar Flare looks pretty awesome on paper, have yet to get one. I had a Bottled Hurricane at lower item level (~815) and it was great all the way up the heroics. The on-use was very strong considering it was a 815 trinket and the radius seemed to line up perfectly with healing rain. As of rite now I am using the Infernal Alchemist Stone @ 850 ilvl. I believe versatility is a very strong and underrated stat, the proc is very strong / happens often, along with the 40% potion / flask increase, I would easily consider to be my BiS trinket as of rite now (pre-raid). Other than the alchemy stone I would say Bottled Hurricane or Thrumming Gossamer, which ever one you can get higher. Gossamer if you want something static / no on-use / arguably better base stats, Hurricane if you like on-use / haste / cool tornado effects inside your healing rain.