Nodes in a map are another factor, but GM_Construct seems to be one of the only maps that has a decent nodegraph. But yes, I would recommend the above.
Get this addon: NPC_AI
Depends what you mean by suck. If you mean they can’t fight worth shit, then get what Ralle posted, but if you mean they just aren’t realistic, they’re slow, inaccurate, buggy, etc, then you’ll have to code your own AI.