I went "Fast" build.
5 Levels in: Precision, Precise Blows, Whirl, Crippling Blows, Fleet Footed, Razor Focus.
2 Levels in: Murderous Precision, Undying (and Strength Training for level requirement)
1 Level in: Arrow Deflection.
Cat School
Yrden
5 Levels in: Poisoned Blades, Protective Coating
3 Greater Reds, 1 Greater Blue. Mix of Quen and Igni Glyphs. Mostly burning and stun runes (though I seldom see them active).
Freya Armour (178, 1 Slot), Assassin Gauntlets (70, 1 Slot +10% Crit %), Assassin Trousers (74, 2 Slots), Assassin Boots (73, 1 Slot)
This is a very powerful combat build, (though a bit weak against stronger monsters ~ I can swap in my Mastercrafted Ursine or Wolven torso armour for only modest reductions in damage dealt but significant increases in armour and resistance).
I can choose to fight "up close and personal" with whirl (staimina use only, in short bursts) (and the 6% per-hit instant kill on the second and third repeats will often do for even serious monster threats - most don't last that long)... or I can work patiently, landing a single hit and evading away for a guaranteed 750+ damage against almost all monsters per hit. (Drowners the most notable exception, but they have no other resistances, so are vulnerable to just basic attacks).
It has been fun since returning to the 'post-end' game to find a "rusty Novigrad sword" and de-equip my silver... still one shotting most mobs (and in a way, that I'd rather see more of in just 'vanilla play'... small amounts of "up front" damage and death some 4-5 seconds later. I'm doing 66-67 damage against "the wrong type of mob". Need to look out a monster with armour to see how viable such a weak weapon could be.) (The problem is that almost all dropped swords are roughly equal to my own "mastercrafted" weapons, so only the "rusty" weapons are still low value. (This also makes it very tricky to find a merchant who can buy even one or two weapons/armours).
Currently have 430kg of luggage (poor Roach).