Flask of fire + thousand cuts every 30 seconds I wouldn't say the tempest is defensive. In fact it probably is the strongest class right now due to the bug.
FoF - CD 32 seconds. Thousand cuts Lasts around 5 seconds or more on tier 3
FoL - Lasts 8 seconds with buffs
FoF - Lasts 10 seconds with buffs
so for 23 seconds you will be invulnerable and have a whopping 38 hits x 300% weapon damage + other damage sources.
All you need to do is not die in the other 10 seconds. Pretty crazy
You base the whole specialization, and my point, on a clear bug? Nice.
FoL is no damage increase. You'll get off 3 attacks within it, then auto attack. So much fun!
FoFro is a small damage increase via shatter. Max 2 shatters.
FoFir is the only damage increase, and it's outshined by assassins Mark of Death, or artificers passives. So, about 3-4 attacks per FoFi?
If we want to talk exploit and cheesing, then sure. But then again, why would you need to? Craft some masterwork tier 3 stuff, and every specialization will kill any dragon within 5 seconds. Yay. Fun?
Or, you could range cheese and kill every high dragon at level 3. So much fun!
If exploiting is the goal, why not just push it down to casual as well? Then we surely will have a lot of fun!