I think so, at least I used it more. Ice will freeze enemies which you can then Shatter Combo with Twin Fangs or Deathblow. I could be wrong, but although the description says enemies who attack you get frozen, I was pretty sure it's just enemies that touch you, so I'd use Ice Flask and wade into a group of enemies, then shatter them with Deathblow. Fire Flask is your #1 stunna though. For big enemies, whittle them down until you get them under 1/2 health, then Fire Flask > Deathblow spam and they're gone.
Some Tempest gifs I made of my second playthrough last year below. Absolutely loved the class/spec.
I run all three now, loving this specialization for sure, very happy. Even dragons go down quickly once I whittle them past 50% and unleash Fire Flask + Deathblow.
However, I've encountered some nasty bug or horrendous slowdown when using Lightning Flask. Only has happened on large enemies like Giants, bears, and dragons, but the game slows to a crawl, including my character. Very annoying.
I'm thinking I'm just about ready to finish up the game. Only got the snow area left, some companion quests, then I can just finish the game, hooray. Still didn't get the trophy for Pathfinder, piece of shit. Better pop on a new game.
I gotta say, Hissing Wastes may have been a tad too large, but I LOVED finding the tombs and completing the key for the main tomb. And having the dragon stand between me and the main tomb was awesome.
Edit: I hate Focus. It just doesn't make sense, there have been times when I build all three focus bars to fill in no time, then there are times when I can't seem to build one for the life of me. I fought the last dragon and didn't build a single bar during the entire fight. Also hate how it seemingly resets to 0 when fast traveling, it's super annoying.
Edit 2: just read up on amulets of power, holy shit why did they remove so many? That really sucks :/