Trouble is even the disengage actions are different, I believe. In 5e all of your movement will not provoke AoOs but in 3.5 it's called withdrawal. A full round action and only safe from the first square you move from.

So there's a big question of which rules to follow. I think if by 3.5 withdrawal he's dead if the spider chooses to take the AoO. It has a massive reach. And 95% chance to hit.....

But overall I think 5e is pretty strong at the lower levels.