So after a bit of messing around, I might have come up with a phys Flicker Strike Slayer that looks like it's SSF viable for a league start.

https://pobb.in/RK2FteAPZSMQ

Parameters: 900k+ boss DPS assuming maximum Rage, Pride effect and totems, but no Berserk or Vaal Haste (goes up to 1.5m burst DPS if so). Not that you'd be doing pinnacles on this, but it's a good indication of single target potential. Clear DPS drops to 533k without totems, Vaal Haste, Berserk, or Intimidate, and setting Pride to minimum effect, but is helped along by Tribal Fury's new melee splash.

Weapon: 2-mod Reaver Sword with T4 phys and benchcrafted %phys. Nothing else. (Although a Terminus Est is lower damage (might be Precise Technique's problem) and only Hiltless of the common endgame unique swords is higher damage. Have I gamed the weapon somehow?)

Frenzy generation in single target: 15% Flicker Strike, 8% swords, 10% Mark mastery. That makes 33% which is just ever so under the rate to sustain Flicker on a single target with Multistrike. Quality on Poacher's Mark is a priority to add 5% more for a margin of safety, and with Vaal Flicker Strike, frenzy generation on single target should be manageable even if touch and go. Generation during clear is sorted by Blood Rage.

Defensively, life is a bit low, but Vaal Pact provides strong recovery to the tune of over 50% of life recovered per second (alongside overleech). I've thrown in a bunch of basic rare templates to jack life up to avoid "cheesing" Precise Technique, but I can still get PT to 5k+ accuracy with a couple of accuracy rolls on rings.

Given conventional wisdom on Flicker being absolute arse for a league start, the numbers look too good to be true, being decent offensively and defensively, and without any obvious glaring mistakes I can spot. Some problems/questions I can foresee though:

• Low individual hit damage (DPS is "inflated" due to high attack speed), so mobs might not die in one hit.
• Impale is responsible for a significant proportion of damage, and that alongside Rage needs a lot of ramp, and may compound the problem immediately above.
• Is +1 strikes needed for Flicker Strike? 40% damage to Close Range targets is a nice boost but could definitely make way if +1 strikes is a higher priority. On that note, does +1 strikes allow you to generate multiple frenzies per attack, and is this necessary during mapping? (I assume it's irrelevant in bossing.)
• Despite trying to make the weapon super restrained, has it still been warriored? Most of the unique two-handed swords I checked do less damage, which is worrying.
• Going into boss fights without a "pool" of frenzies may be painful - I'm guessing this can be fixed with a Frenzy-Faster Attacks link in a weaponswap bow and going to town before switching back.
• Seeing as you'll be spending frenzies all the time, you won't get the full benefit of full frenzies, so perhaps frenzy charges should be set at 4 or something instead?

Any others I've missed? Please go ahead and break this as hard as possible - I want to be prepared for the worst, and it's already marginally mind-blowing that the numbers on a league start look this good. I'd rather be disappointed now and save myself the pain of a dud build rather than to have my hopes raised, and it feels like there really should be something wrong in practical play that the PoB doesn't cover.

Also, I'm not super familiar with Slayer, so if anyone can point out something I've done wrong with the ascendancy I'd also be much obliged.