TP is also picked specifically for that, the 3.5 second channel is globally visible, and it's on a 5 minute cooldown. Placement of the farsight ward has a massive visual effect and is a visible ward. The same thing can happen with a stealth ward, but you're less likely to discover and kill a stealth ward. And if a jungler is taking TP, they're not taking flash.
It seems like a lot of trade-offs that end up pretty fair. Sounds a lot more fair than somebody popping out of stealth and blowing you up with no warning whatsoever. 3.5 seconds is an extremely long time to react to a counter-jungle in this game. In fact, it wouldn't take much longer than that to simply walk to the enemy red from mid lane, and you're likely to get longer and more reliable notice from a teleport.