Tasker is great. I use it for a lot of things. That being said, Tasker (like many other apps) does not yet have support for the 4G switch on the Photon. (The 4G switch is supported by things like widgets on many phones yet. The people who write the software don't usually add support for something until they see that there are a bunch of devices to make use of it.)
I would suggest sending an email to the people who write Tasker asking them to add support for the 4G switch. (I did.) The more emails they get requesting something, the more likely they are to work on it.