The ordinary skink priest has his re-roll save bubble and that's it. It's a very good trick especially with priestly trappings,but with his mediocre statline & the seraphon lack of prayers, which priests of other factions do get, it is indeed a tad underwhelming.
As for the Knights, I'd actually stick with 3 units of 5, it gives you more manouverability & since your opponent isn't going to field large units either you're going to have difficulty attacking a target with more than 5 Knights at a time anyway.
Also, why does your last list only have 2 models and 6 command points but nothing good to spend those points on?
At this point level I'd go for one of the following
Knights based:
Skink starpriest 80
Scar vet on cold one 100
3x 5 Knights 270
An endless spell of choice
450/500 + 50 left for the endless spell
Probably the most rounded option.
Guard based:
Skink starpriest: 80
Skink priest with priestly trappings: 80
3x 5 guards: 270
Emerald swarm 60
490/500;
Provided your opponent doesn't bring 500 points worth of mortal wounds this should be a fairly sturdy list with save re-rolls and healing. And the healing should mean mortal wounds shouldn't just decimate you.
Razordon based:
Skink (star)priest: 80
2x 10 skinks: 120
6 razordons in any unit size combination: 240
1x 3 skink handlers: 40
480/500
Some razordons could be salamanders, but I think at this point level razordons will probably be better due to the larger amount of attacks per model.
Ripper based:
Skink (star)priest: 80
2x 10 skinks: 120
2x 3 rippers: 280
480/500
Terradon based:
Skink (star)priest: 80
2x 10 skinks: 120
2x 3 terradons: 240
440/500 60 points to spend on whatever.
The skinks in these last 3 lists are pure tax though given that 10 skinks won't do jack against anything… so if you can figure out a way to swap em for actually usefull batteline that'd be briljant.
There's also the option to go kroxigar based, but those shine against hordes so feels less appropriate here. Or to go for a big dinosaur, but that is going to end up with your dinosaur basicly being your entire army which isn't going to be a lot of fun to play… either your enemy kills the dinosaur or he doesn't and that's about all that the game will revolve around…
edit: And why does my tekst look different again, this is the second or third time this has happenend for no apparent reason...