John makes some good points and I agree with most if not all of them. My experience as an ally went more towards...... when I reinforced them (smaller Clan) during a siege it was ME who ended up with the Lions share of Shards. Kind of defeated the purpose of helping imo. So, after that I went to try and help keep others from interfereing with our allies siege. I'm a lvl 40 whos decently strong, not overwhelming like some but decently and it "worked" about half the time. 

I'm NOT a fan of the ally system tbh. I think it kinda screws the smaller Clans and wish it would be abolished. 

We did end up winning the cvc but it was a fight to the end and we were not sure we won until final score was announced.