Sylvan powers should be less useful against races/classes that are "in tune" with nature in much the same fashion that say primordial vengeance is less effective against certain races/classes. Rangers/druids and wood-elves should either get ubersaves against Sylvan powers or have the effects reduced. A wood-elf ranger should be damn near impossible to get these powers on in my opinion.

That said, it's been awhile since I've had these powers used on me, but I believe bioempathy was changed to be mental damage right? If that's the case you can easily prep for that. Another option is to rank somewhere less well guarded. Emerald definitely is not the place to rank if you want to be left alone by warders, but there are definitely other options for a ranger where they are less likely to be harrassed because Warders just don't travel that far out from the Eastern Road vicinity. The third option is to take their sapling and give it to Scion or Empire (if and when that comes to fruition).