In my limited experience of vaping high VG juices the longer I leave a coil in place, the better it gets. 3 weeks ago I bought an MVP2 with a Kanger mini Pro 3 top, I washed the tank out before starting but still noticed a slightly metallic after taste, by about day 3 that metallic taste disappeared altogether and the coil seems to have improved over time, still using the same coil after almost 3 weeks vaping the same VG juice, I learned a good lesson which is never judge the merits of an e-liquid using a brand new tank, give it a few days at least.
I use all VG as well. I find that if I give it a few puffs without hitting the "fire" button, it gets rid of burnt taste and keeps the wick in the coil area primed a lot better. Just my .02 cents...