25 range still can't compete with big guns or energy weps and plasma nades are a pain in the ass to make. Plus its not like plasma nades are the only throwing weapon, you can't claim that the other ones are anything but seriously underpowered.
Either way it wouldn't unbalance pvp because pvp isn't balanced, everyone goes minigun anyways.
So reduce the damage a bit on plasma nades, either way heave ho is a useless perk and needs to be reworked.
Since throwing range is str*5 and most ranged weapons have a max of 15, this perk only has an effect if you have 1 str."Each level of the Heave Ho! Perk gives you an additional +2 to Strength (up to 10,) for purposes of determining range with thrown weapons only. This Perk will not exceed a weapon's maximum range. "To have a perk that only does something in that one circumstance and has multiple ranks for no reason is stupid, so to make this perk useful im suggesting that the bonus to range extend the maximum range of the weapon. Since 10 hexes x 3 would be way too far to throw a grenade i suggest each rank adds 5 hexes of range to the max range, or possibly one rank that adds 10.