My Meta has a lot of heavy stuff right now, so I tend to focus more on the heavy pieces. Plus, nothing says loving like a Bronze Back in the opposing Warcaster's or Warlock's face!
The blood runners would give you an early jam unit, so there is that with them. Although with the Gatormen you have a nice tarpit that can also clear out infantry (not super common, in my experience).
As for what I would replace them with... hrmm. I do like running a Krea with Rasheth, because it makes him effectively immune to most scary ranged infantry (gun mages, mage hunter strike force, etc). That leaves a point - which I might use to max out the beast handler units. But that is just me. I tend to prefer to run him a little beast heavy, because I know I am going to lose one or two early on.
I would be very interested in hearing how it works out. I still don't own the Archidon, and Rasheth is one of the Warlocks I am interested in trying it out with.