Soloing War was pretty easy for me from like 1-12, then after that, it became very difficult. Didn't help that I used a scythe, which is god-awfully slow. Logic to upping scythe was to use it to level my DRK. Anyway, after sub job, subbing with WHM helped a bit (just for healing purposes), but really didn't help that much. I added some accessories to increase my MP.. but wasn't too great.
As for WAR being over powerful, no. If you play WAR correctly, you can do mediocre at best.