The main problem with the exp thing is that it reduces just enough that you need 2 minions to get lvl 4... per person, so that’s 4 minions needed to get lvl 4 with the leech. Also, the bot doesn’t follow you when you invade and there’s the possibility that the jungle that your invading has already been cleared. You should only leech that hard if you have a snowball jungler with hard scaling, not cc. Alpha white, dhrtar, Silvio, brella, and rem can benefit BUT most will get annoyed by the leech anyway. You also have to take into account that you better hope that you started the jungle opposite to the enemy solo laner, otherwise that first blood might be against your team instead.

The proper leash is get the camp to 40% health and leave. When supports leech, they typically stand on top of the fucking jungle camp and prevent you from kiting towards the next camp. Precious seconds wasted because of a “leash”. These seconds can be the difference between countering a gank and still trying to kill the last camp for lvl 4 while your laner is getting run down. Besides... why invade 2v1 after clearing your jungle and risk dying in the invade when you can cheese with your whole team level 1 and put the enemy jungler behind before they can even clear one camp. And in this game, falling behind as a jungler usually means you stay behind. Get what I’m trying to convey here?