The 'dry season' in the Maldives runs from December to April, so if you want to avoid monsoon rain, I'd go then. However, it is ALWAYS hot (and regularly humid) in the Maldives: this might be something you just need to take on the chin. For the best compromise between dryness, sunshine hours, and manageable daytime temperature (approx. 30 degrees celsius), I'd say mid-January to the end of February is a good window to aim for.