Now, I can see why it isn't exactly like deafen, but I mean it can be saved against why can't it be a little tiny bit spiffy and atleast more annoying like deafen is.
Like making people yell and all in caps, and not allowing them to recieve tells or similar?

Yar!
Sorry if this isn't very coherent I'll edit it later if it doesn't make any sense

But bard deafen already does what you just suggested. If they are deafened by bard deafen they can talk/speak and it comes out in caps. It also makes it so that the person deafened can't hear/receive tells. The only thing different between bard deafen and all other deafens is that it doesn't stop the person from casting.