I confirmed that George's 5% damage works fine. The issue here might be that you have already put five skill points in the Damage passive, in which case George's damage buff is nullified since only the highest buff counts.

eg. If you have damage passive 5% and you use pet with 10% damage, only 10% damage will count.


It's a bug on how the buff/debuff mechanics currently work. Devs have mentioned they are planning to change that in a future patch though.