Please offer some advice.

I can't beat the Verjak campaign on Champion difficulty in Heroes of Might and Magic III½ (specifically, getting 1 town before the AI arrives). The AI arrives on day 14. Is the problem with me, or are the pirates and rogues just too strong?

I don't think the problem is with you, but with the game itself. The campaign was designed for the original Heroes of Might and Magic III. Not all maps can be beaten on Champion difficulty in the expansion. Not all strategies that work in the original game can be applied in the expansion.