The Vikings are hard to complete, but now it is even harder with a lot more stones on the map. Don't they want us to be able to complete this game attachment?
Of course it's possible to complete - the impediments are meant to be a challenge, as without them, it would be so stupidly easy to finish that Inno would be further ahead to just outright give you all the prizes just for clicking the "begin" button.
The main prize - Yggy Tree is impossible to miss... just completing the settlement 15 times, regardless of how long it takes will get you the ultimate reward for this feature.
The 'timed' prize which is the Greater Runestone is a 'nice to have', but not game-changing in anyway... you can build an incredibly over-powered city without it.
The timed prize for the Japanese settlement is arguably far, far superior, but thankfully, the existence of the Merchant makes finishing it within the time limits almost trivial.