We did the math and you are usually better off having more models in a larger unit or more chaff units than paying for combat poison on skinks. Poison is really only effective and worthwhile on a special unit of skinks deployed to face off against units with greater T but a less-than-impressive armour saves. Terrogheists, giants, greater daemons, beasts of nurgle, ogres, trolls, and stuff like that is what those skink units with poison are designed to take on by getting in the way of them, standing and shooting with poison, and then getting off some poison wounds in combat before they die or flee. However, since shooting with poison shots is about as effective as getting in combat in terms of causing wounds to such models, the poison ability in combat is generally only to increase the possibility of wounding the model if and when charged and not for charging, unless you think you might be able (with the low LD) to force a pursuit of fleeing skinks and, thus, pull the unit out of position.
The premise of the initial question kind of expects more from saurus than is intended. With a few notable execptions, core units in most army books are really not supposed to hold up well against elite special units like execs, white lions, etc. They are best used to do some damage and take some wounds, maybe hold for a turn or two of combat, and support your primary winning units. With the right use of chaff, you can slow down the elite special unit block, maybe reduce it a bit, and perhaps get those salamanders on a flank to shoot down the files of the unit to cut it down a lot further (salamander flaming template hits a unit of trolls, which we are seeing a lot more now including with Throgg recently in WoC armies, and takes away regen and then shooting wounds caused by skinks cannot be avoided). We are seeing saurus unit get so targetted and beat up anyway, that serious consideration is going into just running a lot of skink chaff and MSU units, maybe one or two with poison combat and one or two with a single Krox for LD plus punch if in the flank of something.
While lions are a unique problem because of their special boosted white lion cloak +2 armour save to non-magical shooting, use of BOTWD banner to protect against most magical attacks, and the frequent ward save boost from an Annointed in the unit and the High Magic lore attribute when a mage is in the unit. Poison skink shooting and even salamander shooting has far less effetivelness against white lions than, say, executioners and other elite infantry units. When in combat, saurus have issues against white lions due to striking second with the white lions (especially in horde formation) hitting on 3's and wounding on 2's with no AS left for saurus cutting down too much of the unit unless you run it narrow with spears. Also, the footprint of 25mm saurus against 20mm high elves is a small advantage to the high elves. The saurus get 2 attacks each but are only hitting on 4's and wounding on 3's with the white lions still getting a 6+ AS and ward save. Worse yet with a hand of glory +2WS on the white lions, the saurus can be hitting on 5's in battle. That being said, running a saurus unit suidically into the white lions or taking a charge by the white lions (if the saurus can match width to max attack the mage) just to take out a mage is actually a good strategy to cut into the white lion unit's ability to boost its ward save and also to give you an advantage in the magic phase if you have no characters in the saurus unit or the mage does not issue a challenge. Also, the saurus will cut down some white lions before combat with another unit.
By contrast, white lions against TG can be a decent matchup if you can win the magic battle. TG wound on 2's and at least cut through the AS of white lions. Delaying combat, it is often possible to eventually get arcane unforging to take off BOTWD and then fiery convocation reduces the white lions and you can then swap unforging and fiery convocation spells for augments or hexes in anticipation of combat. With TG. you can protect the slann with a champ and fighting characters while the white lion unit mage(s) often can be attacked directly and killed right away because the mages rely only on a boosted ward save (max 3+) . If you manage in combat to get miasma on white lions or hand of glory on TG or both, then you can flip the hit rate match up often to TG hitting on 3's and white lions hitting on 4's and also, if boosted, you might get lucky and strike simultaneously or first. Rolling into earthblood can also be huge in terms of reducing the loss rate of TG (most white lion units do not have flaming) as well.
To illustrate, I saw a LM army saurus unit forced to pursue a chaff unit of archers i(that charged the saurus for that purpose) into the path of a white lion unit and get decimated by the white lions (to the point of having to roll double 1's to rally when they fled) but the unit managed a wound on the lvl 4 mage and to kill some white lions, just enough it turned out. The LM player had gotten off arcane unforging to take BOTWD earlier and, thus, was able to use fiery convocation (IF, but used soul of stone and slann on flank of TG to limit the damage) on the white lions to further cut the unit down (which reduced the number of attacks the horde could put out once in combat) rather than immediately charging into combat with the TG. At that point, the white lions had to charge into combat or risk dying to spells and really took a lot of TG out in the first round of combat, but the mage got killed and that opened the door to a combo of miasma, hand of glory and earthblood, with the high elf player only able to stop the first spell.
There are issues with the big skink units because they are not quite cheap enough to be used like Skaven use their slave units. You end up putting a lot of points into them and might as well just break them up into smaller chaff cohort and skirmisher units for a better bang for the buck in most battles. The really big skink unit can be run wider as a horde against some units and models, especially monsters, because the wider formation will max the stand and shoot poison hits when charged and when able to move in shooting range and also gives you more attacks back to maybe do something in combat while still remaining steadfast. Against some elite infantry units and high armour save units, by contrast, you may want to just limit the attacks on the larger skink unit in combat and max the possilble staying power (remaining steadfast) and ability to hit back to exploit the narrower 20mm base of skinks. The biggest issue with skinks relative to saurus with this tactic is that skinks have terrible LD, even with cold blooded. So, you might as well go with a saurus unit of smaller size because it can at least hit back harder and is more likely to stay steadfast as long or longer in some metas. I've even thought of putting a crown of command on a cheap skink priest or skink chief in a smaller or modest sized skink unit with full command and run the unit only two models wide (conga line) so that the character is never in the front rank and always on the flank protected from combat. The number of skinks lost in combat is minimized and the long unit length will often keep the unit just in range of general and BSB (often the slann). The benefit of the skink priest is he is often in range of something with PF and able to cast spells but, if done right, able to hide from combat for a longer period of time.
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FFS
