A "donut hole" is a typical trait of just about any light that uses an XP-G emitter with a smooth reflector (a good example of this is the Quark Turbo). In fact, if I'm not mistaken, the donut hole problem was such a big factor with the EagleTac T and P series lights that use XP-G's and smooth reflectors, that some dealers won't even carry these lights with smooth reflectors (BTW...I have a P20C2 MkII, and LOVE it!!!). A good rule of thumb is quite simply XP-G's and smooth reflectors don't play well together. I had a Quark Turbo and loved the output...but the donut hole drove me nuts!
There ARE exceptions to this. If I'm not mistaken (and I can't speak from experience because I don't own one...), I think the new 4sevens Maelstrom, which uses an XP-G and a smooth reflector, doesn't have a donut hole. I'm sure there are others as well, but for the most part XP-G's and smooth reflectors just don't get along very well. If you're going to use a light with an XP-G emitter, OP reflectors are the way to go (in my humble opinion, anyway!), As always, YMMV...
PJD