There are two druids in Gedyneith on Skellige who are designated as quest givers (!). One of them is a bit of a joker who gives a side quest (if you have completed the quest you will know what I mean). The second druid just acknowledges your presence without giving a quest. I have gone to him on several occasions at different times of the day but he never offers a quest.

I have now completed the game and returned to Gedyneith. The druid is still there and marked as a quest giver but still does not give a quest. Am I missing something or is it a bug?

I think this is a bug. I've never been about to work out why that exclamation mark is there after 3 play-throughs.

If you talk to him before talking to Gremist, you can ask him about Gremist & get the quest Advanced Learning (or something like that) & then the quest marker disappears.
If you talk to Gremist first, you get the same quest, but you can't talk to that druid later and the quest marker remains forever.

If I recall correctly, I already had the Advanced Learning quest in Act I way before I even got to Skellige by talking to the halfling herbalist (I think) who lives not far from Keira Metz. It was a dialogue option present during the trading process with the herbalist.

Thank you for your reply and clearing this issue up. It really bugged me that this damned druid was the only outstanding quest giver (!) left on all the maps. I will try this when i eventually do my next play through, which will not be until all the additional content has been issued and a few more patches released to clear up some of the bugs present in the game. I love the game but I find that it has a lot issues I find frustrating at the moment. In the interim I may well go back and re-play the first two Witcher games once more.