Yikes, I use Artistic Wire as well for my silver plated pieces. Is it the silver or gold that is tarnishing? For the gold- which is actually just coated brass rather than plated metal- once the coating wears off the brass is definitely subject to tarnishing.
I stopped using it a while back because the batches my local supplier were getting it were super discolored (almost green? ugh.) and I had to find a new wire source. I started using non coated red brass (found a seller on ebay) the wire is beautiful but it will tarnish- but I include a polishing cloth with my orders and you can rub the tarnish off super easily.
With that said- I'm now sampling a new wire for my gold plated option- Bead Smith craft wire. It looks and works beautifully but I can't speak for how it hold long term yet. Anyone out there use it?
I think it's best to offer a gold filled option to your customers as well, it costs more but I think it's worth it because it lasts much longer. Hope this helps some!