No. 5 bonus damage is pretty much always less than 10% AD. It's strictly weaker at 1-2 trophies, then continues to be weaker until you have 20 - 50 bonus AD. The kills necessary to get to 3-5 trophies will virtually always give you enough gold to put yourself above the AD threshold, unless you managed to kill all 5 of them before you got any farm whatsoever.
So, no, in no real game situations outside of a level 1 pentakill is this a compensation buff. It makes Rengar strictly worse. Compensation buffs have the potential to increase a champion's power. This doesn't in any real game. It's a nerf, through and through.