What is more important in general?

The potential +20 weapon ias using a greater/runic talon, relatively to most other claws

or +2-3 so phoenix strike, or other used martial skill?

I would guess the IAS is more important, but I have read previously we use fade anyway, because the IAS is already too fast and dmg got wasted.
Or this effect got fixed due to last pach about NHD ?

The weapon speed is more important - mostly for building charges. Once you have your charges you don’t need to worry too much about dmg since you’ll be over killing in 1 Dtalon anyways. If any skills, get phoenix strike on your claws.

You can also just use burst of speed while getting your charges then back to fade after that