Changing the exhaust cam makes a bigger difference. The engine flows better. If you change just the intake cam, the engine is still plugged up on the exhaust side.
I'm surprised your bike didn't lose power changing just the intake cam. The 2012-2015 WR heads are different than the YZ450F heads the intake cam was meant for. That is probably why your swap didn't work better than it would have in a pre 2012 WR450F.