Cookie persistence: URL or Domain: which is optimized for LB management?

Yes, but if you separate the applications into different pools with different monitors, so that if one application fails on a server, it doesn't necessarily affect the services provided by the others, you may get better scale. If you take an entire node out of production because one of the three services has failed, that seems less efficient. The only caveat is whether or not one application is dependent on another application ON THE SAME server (ie. local tokens, memory space, etc.).