Thanks a lot to all of you for your answers.
Indeed it took some time for me to figure out that many spells were absolutely garbage at high level (such as fusion missile - unless you use a certain relic - or exploding dart). So at the end there are less spells to play with. In my case it is (putting aside AOE) Tracer Missile, Electronet (yes many guides still say it must be in the classical rotation), priming shot, heatseeker, blazing bolts, rail shot and the pew-pew filler (don't recall the name). Aside from that there are the "offensive CD's" with the supercharged xx to be used sometimes as often as other spells if I understand well.
For that matter I use this guide I found :
https://vulkk.com/2020/08/29/swtor-6...de-by-endonae/
So yes less spells than expected but a bit more than my Havoc DH
- nothing insurmontable !