This IS the most problematic thing about the current PD condi thief in pvp.
1. Make the flip skill repeater a one time use, just like the flip skill for s/d (imagine larcenous strike 3-4 times in a row......just imagine)
2. Increase the flip skill cost to 3 because it is the right thing to do when you nerf thief skills. You didn't truly nerf it if there was not an increase in cost.
3. Put a bit of a cast time on shadow strike, maybe make it 1/2 sec, or 1/4. If you go with 1/2 beef up the initial damage from the strike to make it worth it.
The venom share mechanic needs a rework.
Think about venoms like the thief carrying around a vial of venom. Potent stuff, but they share the bottle and the potency is therefor decreased.
So, make venoms stronger alone, but with shared application reduce the efficacy for each ally shared with such as a reduction of 10,20,30,35,40% (for 1, 2, 3, 4, 5 allies shared).
Soon™ ( ͡° ͜ʖ ͡°) nom nom nom🥔