Phytogenic Insulators themselves are HV/EV tier machines, since they require mana infused ingots to make, so this only really matters for the midgame. This doesn't break balance too much, as if you have the Sapling Infuser augment, you can already farm leaves to make plant balls, and could already farm slime from DSLs anyways, really this just adds an alternative method. (Imagine farming rubber from farming Isoprene, that sounds like the most inefficient way to do so). If it does break balance, then just change the recipe of the Sapling Infuser augment, or something.

EnderIO farming station is generally what people go with for trees, as it is extremely effective. Alternately, yes, people do sometimes use the Slime DML model to make rubber. I would be surprised if anyone who's ever played the pack unironically made rubber from isoprene.

It probably wouldn't hurt anything to add it to the phytogenic insolator but I don't think there's much demand for such a thing.