No, i wouldn't say that High Elves are "overpowered"
I've been in the hobby for 18 months now and mostly use my High Elf army, never won a game.
I can say from experience that High Elves can suffer a great deal from an Isengard army.
I've got a sheer lack of infantry in my Elves army, so I have to fill in the gaps with tons of heroes. Even ones like Elrond and Glorfindel, Lord of the West get slaughtered by my friend's Uruk-hai.
Uruk-hai have a good strength value and are rather cheap in points (for thier profile), so you'll have a good sized force made up of strong models. Use a mixture of crossbow armed uruk-hai, scouts, uruk-hai warriors and throw in some Warg Riders and Berserkers. Make sure that you've got an Uruk-hai captain in there as well. Using Grima can also help, he stops your opponents using Mght as much. Try and get the Uruk-hai crossbowmen to shoot down some of the high elves early in the game. With the high defence and the high strength of their crossbows they can do some serious damage before the first combats have begun.
Hope this helps.