That is the problem, Burgon and Ball shears are made of softer metal than some, the best make are the South African Rosa shears which are harder steel so hold their edge better.
No, it is not recommended to grind the bottom side of the blade, you can rub gently with an oil stone to take the burr off after grinding, you can also swag them (grinding from the flange on the opposite side of the blade to the tip) so as to reduce drag in the wool.
Hope this helps,
Philip