Ulting from one lane to another is hard and ideally you would be shooting from fountain because that's significantly easier, but it definitely is the right call to make at times. If you hit a solid arrow a bad fight, say a 2v3 because their top and jungler both came mid to countergank, is suddenly a winnable situation. In that kind of situation you actually have decent odds of hitting because you have three targets in the lane, and from the distance you are firing from you are more or less taking somebody out of the fight from the sheer duration of the stun (3.5 seconds). Is it a play you always make? Of course not, but to say you should never do it is just silly.
Sure it takes away a lot of your kill potential in lane, and makes you easier to kill, but that just means you change your playstyle for the duration of the CD. Play safely. You have 600 range, AoE slow potential, and a scouting tool so it really should be hard to play it safe for a minute and a half. If the play works out, you just gave your team a huge advantage, and got some assist gold to boot.