Personally, I don't think that that Hariyama would work well without too much babying. First you would need to get some spinner out on the field to get rid of any Spikes/SR/TSpikes which would really hurt Yama. Next, you would have to get rid of any harmful weather effects, so you would need a weather changer. The above two steps would take four turns alone (switching into each pokemon and using RS and weather changing move). Then, you need to safely get in an Agilipasser who needs to then safely pass an agility to Hariyama. That's another three, so seven turns total, assuming the worse case scenario.
Of course, I just realized that you could just lead with an Agilipasser to alleviate most of those above problems...
At any rate, weather can still mess you up bad, as can priority moves. Hariyama already won't last more than five turns, assuming the best conditions. If someone switched in Abomasnow, TTar, or Hippo on your Belly Drum (for whatever reason), Yama would be effectively done for and only get in one or two attacks.
That's just my two cents on the whole thing, anyway.