Even if they are not always followed or if the policy is seen as ineffective, the arms ban is still a relevant symbol. Bans are an important symbol for the international community and it shows a world wide consent that the countries policies are negative and should be curbed. Therefore, the ban is still a relevant symbol.
Yes, the EU ban on arms sale is a relevant symbol of a lack of tolerance for China's human rights abuse. It is important to allow China's economy to develop through trade, but still have a way to take a symbolic stand against China's human right abuses. The ban on arms sales allows for this and also provides a method to prevent China from gaining too many weapons.
The EU is selling weapons worth billions to china every year, mostly dual-use equipment (i.E germanys MAN and MTU are selling motors for trucks and submarines, france is selling hellicopter engines etc etc)
"Most of Beijing's military imports last year came from Russia while France, Britain and Germany supplied 18 percent, SIPRI estimates"