After looking at some data, I'm going to have to walk back a statement I made earlier in a comment.
I think upvotes and stars are just a function of views above a certain threshold, so there's really no extra information added.
That might not be the case. Views, votes, and stars are certainly positively correlated, but not as strongly as I would have guessed, and using only one of these parameters might not tell the whole story. (For example, a question might have an inordinately high number of views, but relatively few upvotes and stars. This might indicate that the question is linked heavily from outside the Stack Exchange network, so a lot of viewers were unable to vote on it.)
Here's a Data Explorer query for Views, votes, and stars for Great Questions. If you plot the data, you can see that a positive correlation exists, but not a particularly strong one.
Views and Upvotes: 0.529
Views and Stars: 0.364
Conclusion: It may be worth it after all to include all three parameters in the "delete votes needed" algorithm.
There are caveats.
This is a very rudimentary analysis. You might get different results if you looked at questions in different ranges of votes. I'm only looking at those questions that have a Great Question badge, since they would be the most controversial to delete.
This data does not include deleted questions. It also ignores whether a question is currently open or closed. These impact whether or not you even can cast a delete vote on a question, so looking at a more specific data set might yield different results.
This is not a labelled data set. To do this analysis right, you'd want to compare questions that were deleted (correctly) to those that are not to find which parameters can be used to best determine which questions should be harder to delete.