The ranking seems about right, though there are many things to factor in so a strict ranking is a little hard to make.
Energy is clearly the king of damage type no matter how I look at it. No immune enemy, almost never resisted, there's a way of reducing enemy resistance without feat investment (polarization).
Electricity and acid feel pretty much the same to me: not resisted by a lot of enemies, but there are few immune.
Cold and heat are both in a pretty bad spot were investing exclusively in those damage types might result in a soft lock. But a character using heat or cold generally have access to both so it is okay-ish (Metathermics and Chemical guns being the main sources of heat/cold)
Bio is too weird to be ranked. We don't really care if enemies resist bio as long as it hits, to apply contamination stacks. The only bio damage we care about is poison and it bypasses resistances. Still, there are a few poison immune/bio immune, so I guess it should be low on the list.
Mechanical is weird too. It is by far the most commonly resisted damage type, but there are no immune. So pure mechanical is possible, unlike most other damage types.
