well the bad news is that plarium isn't going to change a thing about this because his skill is working as intended (and honestly, any change to it would hurt the players far more than it would help them. paragorn is essential in a number of setups). the other bad news is that this is far from the last time you'll have this problem, as he shows up in a number of faction wars levels.
that said, it's honestly not a huge problem. it's fairly easy to counteract with any cc skill (admittedly, sacred order has terrible cc) or with buff stripping, blocking, or stealing effects, as well as a few other less common abilities. you can also just select a different champ at the beginning of round three and then toggle the target over to paragorn after he uses his buff on the first champ. it doesn't take you out of the equation entirely, but it's a lot faster than going full manual.
if you don't particularly want to do that, i'd suggest just running stage 5. the difference in the rewards you get is negligible.