[thejeff]

And by the time rainbow pretenders are casting globals they tend to be safely ensconced in castles well inside their own dominion with bodyguards and surrounded by other commanders and mages so they're hard to target. And domed a little later on.

Rainbows have plenty to do in the lab. After the initial site searching that's what they're for.

Sure it's all your eggs in one basket, but it's a tough well protected basket. It's also the only basket you can design to cast the globals you want cast. If you've got multiple mages with the same path levels, sure use different ones for added security, but if not don't worry about it.