drill speed is a meme
the name of the game on Haz 5 is ammo efficiency and being able to effectively deal with swarms, both of which Driller excels at simply due to the fact that sticky flames is so disgustingly good as an OC they ended up giving a version of it to cryo

all three primaries are insanely good with ammo economy, one flame line/sludge pool/ice trail when properly built turns bugs into a joke and wave cooker is good for killing spitters at range and triggering temperature shock or goo DoT/radiation because of its mods, that and taking full drill speed is entirely redundant because you literally drill faster than your movement speed allows which requires feather tapping and even further heat management just to not end up wasting fuel. If you consistently end up in positions where you have to "drill down" as your absolute best option then you're somehow fucking yourself over