So the Devs closed a thread because I Necro'd it, which I felt was unwarranted as I was providing relevant info. So I created a new post here. Since many people recently used the Lightspeed bundle to purchase SLKR, I figured I would provide some helpful info.
Both SLKR and Rey being the first generation of Galactic Legends are MUCH harder than newer versions. Losing tickets can be maddening. I suggest you Google Gridan's SLKR guide as it works flawlessly. I can't recall (and too lazy to research) if I used his method for the Ult Tier. That tier SLKR definitely should be all health. and bring nobody that will gain TM, as that will ruin his health. Don't follow any else's flawed logic about going offensive on stats.
So, I completed Tier 4 with gear IX SKLR with no issues, following Gridan's video guide. Everyone was speed tuned and I had really good mods (as I've been playing for 4 years). I had to stun Rey and I know you can't do that in Tier 5. That alone may have been the difference, as you about to learn....
I attempted Tier 5 at Gear 10+5. I was 20 kyros short on Gear XI but maxed on tickets and gave Gear X a try...but failed. I had all the same mods, 4 zetas on SLKR and was all health with 78k.
Right off the bat, both Poe and Finn were substantially thicker, requiring several hits from SLKR to go down. But honestly, I thought it was going to be an easy win as I had so much TM and turn swap, that the two were constantly stunned.
But then......whoosh......with one toss of her saber throw, Rey wiped out my whole team except for a mortally wounded, and completely bewildered FOO.
The moral of the story, SLKR must be geared up high enough to survive the saber throw--or gun down Rey before that but that seems unlikely. I did not use the special Tier 5 skill and not sure if that mattered. Although having beat SLKR in my main account years prior, I do remember the Ult Tier special being necessary for a win.