Learning necro, is your hero useless when you fall behind?

Conceptually, I'm not very familiar with heroes that's sole gameplan is to "exist" (aka doesn't have a rightclick plan and just wants to put farmed gold into survival items).

I've experienced two types of polar games with necro. On one hand, you win lane and get a very good radiance timing. You opponents fall apart and have no means to kill you, and the game snowballs from there. On the other hand, you have a rough start and you learn to farm up instead of feed. But you are irrelevant for a long time.

Average timing radiance, bots and shard doesn't allow you to fight. Wraps needs to come in at a good time to feel relevant also.

If your hero isn't equipped to endure one onslaught of enemy bursts then you are completely irrelevant as a pos3. You can never go in first and you are depending entirely on positioning to survive despite having something like a 1400 health pool (during the early timings).

So what gives? How do I play this hero? I don't have a "get in and kill someone/initiate with a big spell" plan like NS, mars and any blink hero. I exist in two modes of either being fat and snowballing or poor and irrelevant. Is that it?