If you only have two sounds going, there's no way they are choking each other unless they are assigned to the same voice.
I'm assuming you're using the main outs? Tempest can work fine on a single channel (or stereo outs), but it really shines as a standalone instrument when used with a mixer. Hihats can easily be higher energy than kicks unless you're on a huge sysyem. I've found the tempest is a really mid-heavy machine, especially from the mains, and ESPECIALLY with distortion on.
Here is my theory on what happens with most tempest users: They turn it on expecting booming kicks, but quickly find their kicks buried in the mix.
Over the past 10 months with mine, I've learned some tricks.
Hi pass everything but kicks and bass. It doesn't hurt to roll off the highs of some hi hat sounds also. Basically, use the filters to prevent frequency overlap.
Second, volume is very important. Kicks should be at max. If you're using samples, you can also keep the volume in check by using the level control in the digital osc. That way, even if you max out the volume on the mixer, your sounds won't get too loud. I've practiced quite a bit and have gotten in the flow of fading in sounds using the mixer on the tempest. This is useful when you're treating the tempest as a straight up drum machine using the main outs only (or in my case, just the L out).
Kicks should be the loudest, and hi hats and snares should be set to taste, but really shouldn't be at max.
All of that said, if you're not using a mixer, I highly recommend it. There is nothing wrong with having your kick on its own channel with a little boost to the lows.