I wouldn't be too worried. One thing i found interesting were the Elf's and how they can take on many soldiers solo. But then i read also that they cant build as many units (or they cost ALOT of resources).
As for orcs i doubt they will be OP. They might have really strong units, but sieging them? It wont be as hard its only wood stockades even if they can build many stockades as I've read i doubt it wont be that hard to attack with good siege equipment. Overall this looks really well balanced i can't wait for this game