I'm not going to get in to the cell phone on a duty belt debate, besides to say that 90%+ of the time my phone is in the car, on the visor, where it belongs.
Otterbox USED to make a "heavy duty" clip that would fit a 2.5" duty belt for some phones, but they stopped. I contacted them when I got a new Blackberry (two years ago) and they told me that they were done making them. I ended up using some pliers to remove the HD clip from my old holster and put it on the one for my new phone. Even though I don't carry the phone on my belt, I thought that the HD clip was far superior. It eventually broke from being streched over the visor too much, and I miss the stupid thing.
It would be nice to see Otterbox sell just the HD clip piece for $5-$10 bucks to retrofit on to your existing holster. It would save them from having to produce a second line of holsters for everything in their line up and it would allow us to replace the clip piece easily if it broke.
FWIW I have been using the Otterbox Defender since 2008. First on a Blackberry Curve 8330, then on a Tour 9630, and now on a Motorola Photon (MoPho). All three products were oustanding, and each time I get a new one I am impressed with how much better their designs get. The MoPho Defender (makes the phone one tough MoPho...no, that hasn't gotten old yet) is incredibly well thought out and designed.