I don't have a degree in CS, though I did end up doing a computer based project in my Engineering degree. Which in hindsight was a terrible mistake, as the level of knowledge of the people marking my work was terrible. However, this coding is something I do in my free time, I haven't been a full time programmer since 1989. My day job is Cloud Networking.
There are almost certainly ways we can improve performance. I discovered the other day we were recalculating adventure ranges stupidly often (every api status hit among other things), and reduced it by adding a couple of checks first. That made a significant difference to speed for me. I know one day I'll find a few days to add a bunch of pre-checks for equipment that improves with the number of parts of a set (Brimstone, Smithsness, etc), which will make a huge difference in aftercore maximizer speed.
The trick is finding them.
I can definitely see SOMETHING weird with Java (1.8_171) and/or Mafia. Not running anything (other than Relay Browser), I'm seeing CPU generally <1%. However, that sometimes climbs to around 25%. When I bring Mafia window to the front, it seems to happen, especially (but not exclusively) with GCLI tab in focus, but it isn't 100% repeatable (leaving Mafia out of focus for a while seems to help cause it). When it does happen, clicking on another tab, or another Mafia window taking focus, does reduce CPU to normal levels.
Edit - Am tempted to find a way to video this now. It's pretty repeatable. Happens when I haven't had it in focus for a while, then switch with Mafia with GCLI selected, goes away when I change focus to something else in mafia, then stays away when I load up Mafia with GCLI.