I spent almost 30 years in the food service industry, starting at the age of 15 as bus boy. I received no share of the tips at that job, small family Italian restaurant, but the servers did well. Most of my time was in management after that. Most of the servers I worked with over 20 years at one of the largest, and originator, of the casual theme dining chains. They were always waged at around $2.13 per hour but would clear up to $1000 in tips on a Friday or Saturday back in the day, with $200-$300 on an average weekday night. The big money shifts were around 8 hours, so on a good night, they made about $100 per hour before tipping out the bartenders (1% of sales) and bus staff, when they were used, at around 1/2% of sales. I have never felt bad about a 20% tip for good service, excellent will get 25-30%. I am also not afraid to tip less if deserving. I do not tip less for kitchen issues, just server issues. After that long in the business, I also have no trouble informing management of poor service, hell, I heard it enough in my early days managing. When I tell the manager, I usually do it after the check has been paid. i am not looking for compensation, just letting them know. If it was so bad all around, I simply do not visit that establishment again.
As for the self serve tap room, I would likely tip around 10% of my check at the end, simply because. If I found out that the wait/bar staff is paid typical server wages and expected to claim a certain percentage of their sales on taxes, that would sway me to at least order some food to justify tipping them. No one tips me at home when they open their own beer, or even if I open and pour it for them. Just my thoughts on the topic