Reasons for taking Saurus is partly modelling (I've converted and painted up 30 of the buggers, so I'll be damned if I don't use them!),
That impacted my thoughts for a while. I have to admit though I find myself underwhelmed by Saurus Warriors. They do well against orcs and goblins, Tomb King minions, and men, but they regularly get schooled by elves, dwarves, Chaos minions, and Vampire counts, at least when I play them.
I used to pay most of my Core tax with Saurus Warriors. Now I tend to take 25-30 and pay the rest with Skinks.
Oh yeah, and I've just remembered another reason to not take Skink Cohorts.
You have to rank the little buggers up without going insane...
I got a gazillion of the old archer Skinks of 5th edition. They rank up real easy.
Sometimes I would army swap with my friend. Embarassingly enough my friend is better at utilizing Skink Cohort tarpits than I.
Pure Skink Cohorts have three main purposes. A very skilled opponent can use 10 man blocks of Skinks as redirectors. They also make a decent tarpit if near a Slann general/BSB. The third purpose is to occupy buildings.
If my opponent and I are playing random BRB scenarios, I like to have a 20 strong unit of Skinks in case of a watch tower scenario. Even if that's not the case, the BRB terrain generator leans towards a lot of buildings. Most of the homebrew generators I created with my friend have a lot of buildings (there are a few exceptions).
When it's my turn to place terrain I like to put a building near but not in the center of the table. If I can occupy it with 20 Cohort Skinks. With a quick to fire weapon they can do a lot of damage and are expensive to charge. That said, I never know what to do with my 20 Cohort Skinks when I cannot stick them in a building.
As for Skink Skirmishers. I would almost never play a game without at least two units. I have gone up to five.
Most people prefer to wield Skink Skirmishers in the minimum unit size. I am a contrarian and I usually used units of 13. The rational is that to panic a unit of 10 Skinks (or 11 or 12), you need to kill 3 skinks with magic or shooting. In a unit of 13 you have to kill 5 to panic them.
But fielding 4 units of 10 costs about the same as 3 units of 13 and you get a whole other unit to play with.
Anyway, my thoughts are 10 or 13 or forget about it. I have made units of 12 when they were escorting a Skink priest but more than once special circumstances made me want to put the Skink priest somewhere else making me regret the number 12.
I once played a
6000 points game, and as an experiment I threw a Skink chief in each of my skirmisher blocks. I made a lot of mistakes but I think the Skink chiefs inclusion was not one of them.
Real life issues including but not limited to Covid torpedoed our plans for 7000 or 8000 point game. It's briefly made me ponder super Skirmisher units of 20 skirmishers and a Skink chief (they would need to lose 6 skinks to panic) but I think they would be a pain in the butt to maneuver.