First you say it's broken and overpowered and then you say none of your examples circumvent any rules.
Either it's broken or it's not.
Just because something is broken and overpowered doesn't mean that it circumvents any rules. It just means that it's broken and overpowered.
You're comparing x-ray vision, time travel, and precognition to being a rat...
You've been playing D&D too long. If in the real world you could change yourself into a rat, you would have a super power that could be helpful beyond belief. You could go on missions for the CIA and plant bugs in almost any building in the world. You could sneak into an area at night, change back to human, do things, change back and sneak out.
You could easily pull down a million dollars a year, just working for the CIA because of how useful and unique your super power would be.
But because everybody and his brother now have magic spells in D&D, giving them out to everyone like candy is considered the status quo. That doesn't mean that doing so isn't overpowered. And overpowered doesn't necessarily mean in a damage or combat sense. Giving PCs the ability to basically scry for free and to escape many inescapable situations and a wide variety of other useful abilities by being a rat has an extremely high utility. Sure, your DM could find that out the hard way and then could throw a bunch of obstacles into your way, but that's just the natural human reaction to something that's overpowered or overused in the game system. Nerf it. Personally, I'd prefer if WotC nerfed every silly unbalancing idea before it got to print, but they cannot help themselves. They really do have no concept of balance and have a very long errata document. Making the power a Daily would have been fine. As an At Will, it can be problematic and disruptive to a given DM's game. Maybe not to yours, but to other DMs.
Anymore, the players are entitled to have every possible fantasy super power imaginable mindset has turned D&D into a low level super hero game. For example, Dimension Door used to be rare and powerful, now it's a dime a dozen. Any PC can get a short range Teleport power and its the status quo. So much for the concept of studying for years to be a Wizard. There's even a Neverwinter Theme that hands out a short range Teleport and it's not handed out to the Wizard (that same theme can have the PC go invisible, there's another theme with Levitate).
Bigger, badder, better strikes again. Balanced? That B word isn't in WotC's vocabulary.
