Well, yeah, but that doesn't mean toss shouldn't run High Templars if the game somehow progesses so far that teching much beyond collosi is viable (which in my experience it usually doesn't, admittedly). Just the threat of them evens the playing field quite a bit. Prior to teching up to Templars, ghosts are the bastards that wipe out half your strike force's effective health in one fell swoop. Post Templars, Ghosts also become those guys who are on Templar duty lest their medivacs get Feedback nuked or their MM ball gets wrecked by Storm. The fact that EMP is so valuable against so many targets almost works against the Terrans just a li'l bit. It almost becomes a li'l bit like an elaborate game of chicken as far as energy management is concerned; EMPing a Sentry is often only a good idea if you've got all HTs accounted for, which can be sort of tricky if toss is stowing guys away in prisms.
But yeah, ghosts are jerks and I hate their faces.