Im not sure exactly how things stack but these traits do stack. Also I think the real "magic" of efficient characters is probably in the middle. Either way its a nice bonus.
Lets pretend that you have an efficient alien main character, a borg BO, and 2 Saurians for 4 stacks at 5% apiece and 20%.
If you were to add 6 ranks of skill points at the 4 effieciency categories it would get you to 40 effieciency on all 4 skills of shield, aux, engine, and weapons. Now pretending that it stacked 5 points per officer per skill then you would be a level of 60 which is higher than rank 9 in each skill even though you paid for 6 ranks of skill. Even if it stacked 5% rather than 5 ranks then you would still boost efficiency by 20% and rank out at 48% instead of 40% so that you would have rank 8 level efficiency even though you only spent skill points for rank 6 skills.
There is a lot of resistance to the skill cap which I think is a good thing. But having 4 or 5 efficient officers would at the very least be as valuable as having an extra 2400 skill points to use in other areas. You could literally buy 8 ranks of skills in a category you would have ignored while trying to rank efficiency up to level 8 in each of the 4 skills it is available.
There is a downside of course. You cant use those very rare bo's that have 2 superior ground traits. Also Saurians are expensive on the exchange. You could probably buy a MK X weapon for your ship for the kind of money it would take to buy a single Saurian. Maybe Tribbles buff you as much anyway, however, I would think tribble buffs would stack on top of Saurian buffs.
For an all out ground build Saurians are useless. For a mixed ground / space build its 50 / 50. For an all out space build then Saurians would seem to give you some flexibility to use points in other areas besides building efficiency skills to 52 and running out of points for weapons / science / and starship operations.
And VR officers arent particularly cheap these days, especially the good ones.
Efficient Saurians are about as special as Rare MK X weapons. They are special but not overbalanced and game changing. You could be happy with a MK IX weapon for your ship but the MK X is slightly better.
Thats how I feel about Saurians. You get a slight advantage and boost if space combat is your thing. If its worth millions to you to pay for it ... might be another matter. There are consoles, weapons, and many other things that would also benefit you.
Still the opportunity to spend skill points elsewhere than on needed efficiency is a nice little bonus benefit of those officers of the Saurian race who arent quite yet drunk on their brandy.
Happy Prosperity All,
Bugshu