Well, let's see...
My experience is that resort buffet breakfasts are madhouses. My experience with Boma closely mirrors yours on both of the occasions we have eaten there. I will say that our waitress really did seem to be doing her best but she was stretched thin. I do have some sympathy for waitresses at these buffets. They are not paid more than at other venues but get practically nothing in tips. For a typical table, these waitresses do (or at least should do) nearly the same legwork as a waitress in traditional restaurant. Nobody's signing up for extra shifts in Buffet land so it's easier to end up with service shortages.
For drink refills, just walk up to where the soda fountain is and ask. If nothing else it will let them know there's a problem
I know exactly where you were. I've only dined at Paddlefish once and service was excellent. Fultons was a regular stop for my family and the service there was good, with only one notable exception. In any case, Paddlefish is a 'signature' dining experience and I would not have tolerated service like you describe. I'm generally very easy going in this regard but when a restaurant calls themselves signature I expect signature service. The second time you spoke with the manager you should have requested a new waiter. I would not have tipped above 10% for service like this.
Oof ... I'm inclined to chalk this up to a simple mistake riding the coattails of your string of bad luck. If it were something more substantial, like an appetizer, I would give the issue more weight. It always seems like putting in the order is a simple thing for the waitress. At your average cafe, it is. But these places have multiple cook lines and stations for salad, soup, and dessert. When things work perfectly divvying up an order to the proper lines is automatic, but often something hitches out and the staff are told to walk orders to stations or another person takes the orders by hand and organizes them in the kitchen till things settle back into routine.
Long story, short... Service like this has been rare for me. It happens, but not so much in a single trip that it makes me question WDW dining as a whole.
Whenever it does happen, always voice your concern to the manager earlier rather than later. It's awkward to ask a waiter to send the manager, actually I will usually just walk down to the host station and make the request. But putting your concern into words early will give the restaurant time to make it right.