Aesthetics aside (totally personal) don't get too obsessed about pannier shape, unless commuting with little stuff, I've always found that our stuff invariably fills the space evenly ish, or at least with careful placement.
but then to be honest, a slight mishape doesn't bother me like it does you.
Yeah a bit of bulging of the load wouldn't bother me either. That said IME, most stuff I have carried packs pretty easily, compactly, and neatly. One exception could be a large sleeping bag that didn't stuff well, but it could be left unnstuffed and stuffed directly into a pannier. I never actually toured with a bag that big, but I did backpack and canoe camp with one many decades ago. The bag I use these days pack quite small and suffices for any weather I want to tour in. Group gear may be another thing that might be an issue, Large pots, big tents, and so on. Tents are something that when I used them never went in the pannier though. They always go on top of the rack. So about the only thing I might ever carry that might bulge would be a great big pot, but I have never carried cook gear for more than 3 and the pot we used wasn't big enough to be an issue.