I'd consider the Itti Bitti D'Lish snap in one nappy as its very absorbent, very easy to use (one piece to go on for the nursery staff) but you can get extra pad sets so drying won't be an issue (the outer dries quickly anyway)
My 6 month old boy is a really heavy wetter as well. I use either Bumgenius V3s (with an Easy Peasy hemp insert, topped with a Little Lambs size 2 bamboo booster, and the BG newborn booster on top of the lot) or a medium Real Easy all in one (old style - with sewn-in hemp insert) stuffed with an additional bamboo booster folded in 2. The Real Easys are great nappies and have a big pocket for stuffing, I even used them as night nappies for a while and had no leaks at all.
We don't have a tumble dryer either. The BGs dry really quickly and most of the Real Easy dries quickly too, it's just the hemp and bamboo bits which take a while to dry.
the fuzzi bunz insert that comes with the nappy is a bit lightweight - if you stick a layer of hemp under it you might find it lasts longer. Other than that a pocket with a more absorbant insert would work - i used to send my ds to nursery in pockets - we mainly used bumgenius, happy heiny, fuzzi bunz though nursery always left them til last as clearly the whole poper fastening thing used to throw them. Greenkids anytimes (not the funtimes as they wick alot quicker) with the bamboo insert are very absorbant. Like Ariela says though the ittis are a good absorbant nappy to.
I wouldn't recommend Ittis for a heavy wetter - I tend to use them when I know I'll be able to change DS3 very regularly and when I'm changing him in front of cloth-sceptics. They last pretty well and are utterly gorgeous but when they leak, they really leak.
With pockets it's all in the stuffing my experience. I'd always combine microfibere with hemp or bamboo in a BG pocket and add an extra booster to a Blueberry. The new Tots Bots easyfits are great and can take a fair bit of boosting too so last well. And Greenkids (Anytimes and Minkytimes) are really reliable if a bit basic.
I'm not a Fuzzi expert or Fuzzi fan but I agree with nappyzone - if you add an extra booster they will probably be fine, just be careful not to overstuff as that can cause leaks too.
My DS is an heavy wetter and is at nursery. I use Bumgenius v3 (to be discontinued) and if they leak it's only because the girls at nursery have not put them properly. They come with 2 inserts. I only use the big one folded and for the moment it does the trick. DS is 5 months.
I agree with Swampster, it's in the stuffing with the pocket nappies. Tots Bots V2 are good with boosters (not on its own though), I use the bamboo booster during the day and a bamboo and other booster (microfibre small booster from Bumgenius). Nappies that work well and are easy: Close Parent Easy dri esp with the bamboo insert.