Im sure there are some legitimate reasons why this would have been changed, but, like the others, I don't see why something this drastic was done. (Read: I'd like to see some dev feedback.)
Furthermore, this basically ruins this line of spells unless you are the only rain class in a group, and the only group in a zone. I can foresee something along the lines of: party A is hunting in a zone using rains, then party B enters and they start to rain. Now maybe someone will simply bite their tongue and switch to other spells, but often you are going to have a nice argument between 2 groups about who can use their own spells to hunt their own mobs. It really just seems overburdening at this point. And of course, raids are another huge problem which have already been pointed out numerous times.