Well, on the Wish, we bought one of the Cooler bags at the station on deck. The guy literally just handed us the bag. No alcohol in it. And we had to pay a 18% tip for that. I think that was a bit much... Not as bad for the $900 tip you have to pay if you buy the Hyperspace Lounge $5,000 drink... (we didn't)
But to your point. We always tip standard, then add some $$ to crew that we think do an exceptional job.
That said, having been on a couple Virgin cruises now, I really, really like their system of all "tipping" being included in the fare. You buy a drink, there is no "tip line" at the bottom of the slip. It's already factored into the price of the drink. We talked with the crew a bit (they are allowed to eat in the "Galley", which is kind of their buffet-type area, though it's more a food court), and a number of them had come from
DCL. Also a lot from Princess, Celebrity and Royal. They all wanted to talk about how much better they liked working at VV. First, they are paid quite a bit more (they didn't say how much) on their base rate, so essentially, your "tipping" is included in the cruise fare and you don't have to worry about it. Another thing they said, and I didn't really think about this, is that they get free WiFi. I didn't realize they had to pay for Wifi on other lines, but the people we would talk to would say how much they enjoyed being able to FaceTime/Skype their families everyday and how much better they felt being able to do that. They also appreciated that VV lets them interact with guests to a much greater degree than other lines (like being able to eat and sit with guests in the Galley).