Yeah but the point is that one unit of saurus can take one charge (then more charges subsequent turns), while three units of skinks can take (flee) from three charges, each one allowing for nasty countercharges from your super-heavy hitters. If a skink unit dies - so what - it's 50 points and he died taking out what is almost inevitably a more expensive or tactically valuable unit. If the fleeing skinks survive then great - go flank, go take a table quarter, go harass or marchblock something or set up another countercharge. In short, the skinks provide flexibility while the saurus do not, no matter how solid and reliable they are.
You seem to have a misconception, the saurus are not good chargers imo, certainly not unsupported. They only have one rank fighting on charge, and I think are best used to receive charges from all but the heaviest of foes. Not to mention that their slow speed limits their use offensively. The carno or the warspear can solocharge most things, and any combination of your 4 sets of beasts should be able to break the nastiest of anvils with mass impacts, carno/oldblood mass attacks, 12s5+6s4 saurus cav attacks or impacts+burning alignment all factored in(provided the chief/priest doesn't die, reducing the respective steg's use by about 1/3). Anything remaining probably lost combat and probably is outnumbered by fear/terror-causers if not VC/TK or Daemons.
The point of this list as it seems to me is rolling everything forward with the skinks ensuring you control combat while the terradons and chameleons hunt war machines, marchblock and take out enemy movement control (light cav etc).
Best of luck, really. I would take the skinks over saurus, but maybe that's just because I'm a big fan of movement dominance.
