My worst troubles on my 7Mb/768kbps line all started during that halloween blizzard in the northest usa a few years ago. It was that storm that started my issues. A line came down and they did a bad splice fixing it. 90% of lines here are copper, there is only fiber on some main lines, none to any homes. The 'fixed' line had 66% packet loss and as a result horribly inconsistent pings. During that halloween I somehow managed to stay in gw, my traffic must have been rerouted to some extent...
I VQed Dalada Uplands with an in game ping of up to 180,000ms, yes 3 minutes, idk how gw didn't boot me out. I would notice my heros stopped and keep going, I would scout where groups were, then what can only be described as "the rubberband from hell" would happen and BOOOOOIIIINNNGGG back to my heros I would go.
Inconsistent internet is the worst, slow but stable is better-ish, best is getting what you pay for. It just plain sucks when they can't figure out the problem. Have you tried something like traceroute? Ping Plotter works better than a plain old traceroute, it does ping and packet loss for every hop with a better gui than a command line interface. It's the only thing that got my line fixed, they kept saying everything checked out fine until I used it and told them exactly what hop the loss was happening at.