Hitting an enemy from behind with Shadow Strike resets cooldowns. There's a couple ways to set it up as a Tempest. First, use Lightning Flask, set position, use Fire Flask, spam Shadow Strike + Lost in Shadows (Stealth Upgrade makes it instant). Resets flask cooldown.
Use Hook and Tackle after using Frost Flask, freeze enemy + take 90% less damage if they do catch you, get behind enemy, fire flask spam Shadow Strike, then switch off to Lightning Flask, Leaping Shot, re-hook, or just walk up, and reset the process again.
Deathblow spam is awesome, as a Tempest. Deathblow's a quirky skill, if you're not using Fire Flask, and you use the second hit (enemy HP < 50%), then it will eat up 45 stamina if you have it left. Under Fire Flask that's no big deal, but if you're not using FF, or you're using an Assassin, you want to time it so you use it with less than 90 stamina, so it doesn't eat up the rest of your stamina (generally for an Assassin, this means using a Flank Attack and/or Twin Fangs before using it).
Artificer doesn't really roll with Deathblow (it's still a great skill on trash mobs), but with Artificer you want the most hits possible (Spinning Blade abuse, and Leaping Shot Spam). Because then your cooldowns reset every hit against an enemy (that's a critical hit). The goal of an Archer Artificer is to get crit chance so high that when it fires off 36 arrows from Leaping Shot, you want 24 to be crits, that resets Leaping Shot's cooldown time completely, letting you spam it for as long as Hail of Arrows last (12 seconds at Focus 1, 42 seconds at Focus 3). Nothing in the game can even come close to surviving against that much damage.
Tempest can use a slightly weaker version of that, because you're limited by Fire Flask's cooldown time, Shadow Strike can help reset that cooldown time. Tempest makes much better use of Shadow Strike than Artificer, because the quick, single hit isn't affected by number of hits under Fire Flask, Artificer makes better use of Leaping Shot, because even assuming no Hail of Arrows, if all 12 are crits, you can remove 6 seconds of cooldown on all your skills at all times.