Out on the subject of the PA/cannon buffs, there's a line that got truncated on the posted changlog, Huge/Advanced PAs got a 14%/10% DPS buff alongside medium/large getting 2%/5%. Remember they're getting increased projectile speeds as well which increases effective DPS notably by increasing hit rates, and that before the end of beta they will also have access to higher end engineer mods (this will hopefully be a server-side change as soon as some wrinkles are sorted out that are hiding quite a few mods).
The primary purpose of the damage changes here is for consistency, for example the small multicannon used to have a ~35% damage bonus for fixed over gimbals, whereas the huge had a 4% - when the range is that large comparisons between fixed or gimballed multicannons as a whole really can't be accurate. But the first step is to make the comparison meaningful, hence the comment in the changelog about further changes probably needed later
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