you think it would've been necessary if they showed one final glimpse of Garth coming back in jasper at the end in A&O 4?

No. Doesn't sound really necessary.

TBH, I wouldn't care if they did that or not. Garth's my least favorite out of the four main wolves. It probably could've made fan's reviews even more positive but what's done is done. At least they specifically mentioned unlike A&O 3. That shows that they haven't forgotten about him.

Not really. I don't miss Garth all that much. I miss Princess more than him, to be honest. I connected to her more than I did to Garth.