There's a lot more to the question than simply whether or not these terrain exploits, as a whole, are "good" or "bad".
If you're talking about a short-cut, that any class could do if the player knew where they are and had the coordination to do them, then that's fine. That isn't unbalancing.
If you're talking about terrain exploits that favor a certain class or a few classes, then that is broken and unfair to use. It invalidates the argument that the other player simply didn't work hard enough to learn the jumps. Any exploit that makes certain classes untouchable is BS.
Furthermore, any exploit that puts a defending team at a severe advantage is also BS. This goes for pretty much every terrain exploit that isn't a simple short-cut. If the flag-holder wants to play keep-away, and gets to one of these spots, he is able to get up there without being under attack. When the flag return team comes for him, in theory they are able to do the same jumps, but in practice they will have to do so while under attack. This means they will get dismounted, for jumps that require being mounted, or simply killed before they can finish navigating the jump.
And these are especially offensive when there are such safe-zones on one side of the map that aren't on the other side of the map. The Horde end of WSG has many more, and much more effective, jumps and safeties than the Alliance side. I notice that there are a disproportionate number of people here who think that terrain exploits are perfectly okay, just as there are a disproportionate number of people here who play Horde. One would be foolish to think that were mere coincidence.
Thus in reality, the only terrain exploits that are really okay are ones that A) only shorten the time to get to another place, as opposed to jumps that are the only way to get to that place, and B) that any class is able to make while not mounted. Any exploit that doesn't meet those two conditions is a dirty trick. Using them, knowing that not all classes or factions can do the same, is BS.