61A is not a weeder course at all. It’s theoretically the CS 102 equivalent at Berkeley, with CS 10 being the CS 101 of Berkeley.
The problem is that because CS 10 is not a required course, most freshmen that come into Berkeley, many who were top of their class in high school, think “hm I can just take 61A since it’s mandatory.” It’s not entirely their fault, since Berkeley doesn’t do a very good job of advertising the CS 10 course. It’s fairly new, and there’s still a stigma around it — that you’re “not as smart” if you need to take it. The result is you have almost 2000 students every semester, and many of them are inevitably going to struggle.
I’ve sat in some CS 10 lectures (albeit while I was graduating with a CS degree and TAing CS 61B) and watched my friends do the homework. I didn’t have the luxury of taking CS 10. It’s a great way to learn how to think like a programmer. My personal recommendation is that every incoming Berkeley freshman going into CS should take CS 10, and it should be made mandatory. The CS degree only takes 3 years to complete all the required courses at a fairly leisurely pace, so there’s definitely room to add an extra requirement. Especially since now, the incredibly stupid EE16B has been dropped from the curriculum.