Drinking while casting in Arenas

Is this considered an exploit?
Blue answer pls.

I dont know how it works yet but trust me if this is not fixed will sread out soon, since works like a charm.

I have seen paladins drinking just after casting holy light, NE druid casting Rejuvenation while they are still sitting and drinking.

You can even see among the buffs of the target the eat/drink 'buffs' while they are casting and after cast they sit and continue drinking/eating

I will do my best to find out how this works, Im quite sure it has to do something with the actions being taken from server to user client, im testing to reproduce it, but I swear it looks like cheating.