You can get some wyvern salve from the friendly dragon elf near the main nest, close to the starting point of the island, which will get them to leave you alone. If you are not up on the ridge surrounding the main nest or in one of the other two nests, I don't think they should bother you, though.
I was level 19, and the level 16 wyverns could not do damage as fast as I could regenerate. I used a bow to take out the ones that got close enough, and a retaliation aura (with a fixed damage) helped with the ones that mostly stayed out of range.
I was almost to level 16 when I reached sentinel island, so rather than waste the first mindread on the island character to go up a level when I only needed 3k experience, I reloaded and went to the Orobas Fjords to level. The first couple opponents brought me up to level 16, and as long as I was there I went down the path, reaching level 17 at the bottom (level 18 opponents). Crossing the water by the falls, and then swimming over to another beach (level 18-20 opponents) almost brought me up another level. I had to take out 4 or 5 level 21 imps to get the last ~4k experience to level again, which took several attempts, even using the creature as a distraction.
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