As a Pos3, how is my team supposed to start fights if I don’t have a blink/stun combo?

Low MMR here. Lately i've been focusing on pos3. I've had a TON of success with Axe, Centaur and LC. For some variety, I want some characters who don't just blink/stun on someone; something like Death Prophet, Necro or Razor. The thing is, i'm not really sure how to properly play/position with them.

As the 3 i've been playing, the idea has been pretty simple. As a general rule it's been:

• We smoke. I blink/stun on either any 1/2 targets who are by themselves or on their core if theyre grouped up.
• We're sieging a tower/HG. I hang to the side and jump someone who comes up too far and team knows who to follow up on.
• We get initiated on. I stun whoever is attacking my carry or their backline.

That general strategy doesn't work as well with the other characters I want to try out. If I try jumping someone with my characters, they can either just walk away or just stun me back and their team bursts me. So how am I supposed to play them?

I'm always the 3rd to pick in the draft. Should I only be picking them when one of the supports is a hard initiator? Looking back at my last 10 games, I only had one game where even one support filled that role (tusk).

If I can pick them even without an initiator, how do I handle the 3 scenarios above? I'll just take DP as an example to use.

• When smoking, am I just walking in front of the group or letting someone with a stun? Am I front lining or kiting?
• During tower fights, do I just need to wait until they jump one of my teammates? Should I be in front so they jump me?
• Counter initiating seems easy enough.

Any advice? Just feels like a totally different playstyle and as a beginner I can't really figure out what it is? I know all 3 of those heroes are decent but at my MMR I don't think i've ever lost a game against them because the enemy team couldn't really figure out how to fight, so i've never had a chance to learn from experience.