where can I improve moste effectively on my trickster?

I haven't played in a while, but the first thing I'd do is get rid of all the skill points below your Blood Drinker, I counted 15. For a few reasons; that Acrobatics is cutting off part of your energy shield, so you have your Escape Artist skill which is boosting energy shield, then you have Acrobatics which is taking it away. Not an efficient use of skill points. You also have five skill points wasted on just +10 dexterity to get to a few notables in your tree, not very efficient either. I'd refund all of those and find some notables that are closer. Unnatural Calm and Arcane Focus would be good, you have some base energy shield points in your build but nothing much in your tree to boost it. So you should see a big difference just in getting those two.

I'm not sure what you're doing with Vortex and Arctic Breath. Pick one or the other because you can only use one at a time anyway. You're better off saving those sockets to set up another utility skill. If you like Vortex then you can combo it with Frostbolt, it will give you more damage and give you some range. You can make your chain something like this; Frostbolt > Multiple Projectiles > Slower Projectiles > Faster Casting > Arcane Surge. Then land your Vortex on your frost balls. I've tried this and it work's o.k but the clear speed is kind of slow.

Or you can set up a six link chain with Arctic Breath, probably your clear speed would be faster.

I'm not sure you need Frost Bomb and Frost Bite, each one reduces cold resist. For clearing mobs one or the other should be enough. You'd probably be better off getting rid of the curse and using Frost Bomb and a totem for your utility skills. You can try a Shockwave totem with Added Cold Damage in it. Or if you are dying too much, use a Decoy Totem.

You're taking very few nodes on spell damage in your tree, spell damage will boost your damage too, not just cold damage. I would get Arcanist's Dominion, as it's only one node away from what you have, then probably Frost Walker. You might be able to redo the path in your tree to make it more efficient too. Then if you have enough skill points left over, get Breath of Rune.

If I remember right, Frost Breath is half on hit damage and half damage over time. So get rid of Growth and Decay if you stick with Frost Breath because that would only boost a portion of your damage. But Vortex is mostly damage over time so Growth and Decay would be a good choice if you want to stick with that. Your Trickster is centered around damage over time, so probably Vortex would do more damage if you combo it with Frostbolt but Arctic Breath will give you a better clear speed.

Thx for the tip on acrobatics. You're probably right that I shoot myself in the foot by using both Escape Artist and Acrobatics.

I'll try to rework the skill tree.

Spell damage also boosts damage over time on both vortex and arctic breath. So I'll work with that too. I use both spells at the same time for rare and unique enemies, because they stack.

And I use Arctic Breath because I don't wanna go totally meta! ;-)

I guess you're right about the stacking, didn't think about that. But I would still put Arctic Breath in a six link then just use Vortex as a utility, maybe link it with Arcane Surge?

But if you want to kill Shaper, probably Vortex comboed with Frostbolt would work really well.

Thank you all for the detailed advice.

The one that made a huge difference to begin with was cutting everythin below "coordination" in the skill tree. Including acrobatics.

I am now much tankier and I hit harder. Yay.

I will work through the list and maybe try the obvious coldsnap and vortex combo. Now that I have played "off-meta" to my hearts content. :D