No, I don't think it's bugged, I think it's working, it's just not written super clearly....and then a lot of people don't really know how percentages work.
From what I've personally seen...and I have 6 alts who all exist for literally no purpose other than doing crew skills, so that my 2 mains can have anything I want at any time without needing the GTN...but from what I've seen, with all the buffs added, the crit rate is roughly 1 in 4 (about 25%).
With no buffs, and a level 1 companion, it's more like roughly 1 in 6 (about 16%).
With the understanding that a crit chance is a percentage (obviously), and we assume that the starting point is some nice number (a fair assumption) then we can follow the math:
Let's say the baseline crit rate is 15%, for a level 1 companion (which is pretty close to the about 1/6 that I've personally seen).
A level 50 companion gives you +75% crit rate. That's not clearly written. You could certainly see why someone would think that 15% + 75% would be 90%. Which we obviously know it's not.
Rather, I think what they meant to say is that the rate is *increased by 75%*. Which is a totally different statement.
When a number is *increased by 75%* is just the long way of saying that the new number is 175% of the old number (100% of the old number is, of course, just the old number).
So we name the original value A, and the improved value B. If we figure that B = 175% of A, that is mathematically just saying B = 1.75*A
So if A (the original crit rate) is 15%, well then A = .15
And now B = 1.75*.15 = .2625
Which means that B (the new crit rate) is .2625 -> 26.25%. Pretty close to 25%, or the roughly 1/4 that I've personally observed. Makes me think it's right.
So no, I do not think the functionality is broken. I think it's working just fine. But the verbal description isn't good, and it can be tricky to remember how percentages of percentages work.