Rifts is really, really bad in that regard. I ran one Rifts campaign and probably won't ever run another one.
Im hearing you.
The interplay of rail guns + autofire, lead to multiple attempts to soak on a single turn from some PCs, presuming they even had the Bennies for it (which they often didnt even if you were throwing them around like candy), and a ton of PCs getting turned into pink mist.
I managed to 'fix' it by changing the way autofire worked (you can either spray an area with a burst making it an area attack potentially affecting multiple targets, or you can hammer a single target with multiple shots inflicting an extra dice of damage). Whichever option you chose, the burst was resolved via a single attack roll with the -2 autofire penalty.
I removed 3RB and ROF and weapons were redone as either Auto, Single shot or Semi auto.
Made it a lot smoother, but then we still had to deal with multiple actions, the quickness power, two weapons (or more) etc. To fix that I had to basically limit each turn to 3 actions (before SWADE did this officially), and amend a lot of Powers and Edges that added extra actions (instead having those powers reduce the MAP).
My next step was going to be giving all weapons a simple fixed damage value that is added to 1d6 (you get an extra d6 for a raise) for damage to speed that up as well, and removing AP entirely.
Then I tweaked how Soaking works by adding an extra wound level (4 wounds = dead), and tallying all wounds a PC gets in a pool for the turn (and applying them at the end of the turn) stopping counting when the PC reaches 4 wounds (and dead), and disregarding any extras. At
that point the PC Rolls to Soak (instead of after each hit that turn). You still need a Bennie, and for each success you can soak a wound you took that turn.
If you took 4 wounds in a single turn you're dead unless you can soak at least one at the end of that turn (meaning you're only incapacitated) Soaking two wounds leaves you with 2 (-2) soaking 3 leaves you with 1 wound etc.
At that point it was running a lot smoother, but I kind of just lost the love for it I had at the beginning.
Really, the system would run a LOT better with a handful of generic weapons with basic stats; like a single weapon called a 'Firearm' with nothing more than a basic two ranges (short and long at -2) and a single fixed damage value (that is added to a d6), and room for one or two traits (autofire, long range, concealable, large calibre, silenced, accurate etc) that you can pick from a list.