No - an ordinary 1/2 pad will not fix the problem of your saddle compressing down onto your horses withers and shoulders.
If you continue to ride in a saddle that is front heavy, your horse is going to end up with underdeveloped muscles and pockets around the withers and just over their shoulders. I can easily pick out horses who have this "physique" .
The pad that was posted, my appologies Kitten_Val - the Diamond Wool Wither Relief Pad, does not work in insances like this. It is just an ordinary 1/2 pad, with just extra thickness. DO NOT GET IT!!
What you need to do, is get a CORRECTION 1/2 PAD
where you can add shims to the area's needed. So, what is going on right now is your saddle is top heavy, meaning too wide for your horse, so the saddle is pommel low and unbalanced on your horses back.
You need to lift the front up, off of your horses shoulders and up off of your horses withers, while protecting the rest of the back from the saddle adjustment.
My fellow was ridden for 3-4 years with a wide saddle and a wither relief pad just like that diamond wool one - and due to that, his topline is horribly weak, and he has massive pockets at the base of his withers just ontop of his shoulder area.
By throwing a basic 1/2 pad into the scenario, you are not fixing the issue, you just added extra padding, and the saddle is still going to sit the same way on your horses back with it, just as it does without it. The weight bareing still occurs on your horses shoulders and withers - there is no change.
That is why you need a pad that can help adjust the saddle's position. By getting a pad that can have shims added to the areas you need, helps fixing the issue.
BUT just as upnover said - you need a saddle that properly fits, without having to use gadgets like Correction 1/2 Pads to "mute" the real issue.