In my personal opinion WHM and BLM have alot of downtime, but thats simple to fix. Go out and fight some EM to get use to job quicker, you may lose exp, but if you get use to the job it's easier to handle. Sounds kinda dumb but it works. It's what I did for RDM till I got use to it. They dont got much downt time, or I dont atleast cause I know how to conserve MP, but even so. Just fight some EM and get use to conserving MP and learn when and when not to cast. Thats the easiest way to do it imo.