Sunny and I went back through the items you pointed out. Somethings we had basically said the same thing and we just fine tuned our words for clarity, there were some good gems you pointed out and we added those as needed.
TK is a underpowered army with some overpowered units, and yes there are trap choices. Many of the units ended up with yellow ratings because of this. Yellow means that you need to consider its use and synergize the choice with the other units you take and your play style. So, those units that are yellow would be just that.
We do try to consider the broadest of possible application and potential when rating and providing advice on that unit's role. Obviously we are only human, but have a lot of experience between us, come from different playstyle backgrounds and have competitive peer groups that put things we find to the test. So a lot of advice is directly from that first hand experience or from our peers who have made these tactics work.
No, of course. My point is simply that Tomb Kings are a cruel mistress. From the outside they look cool and have plenty of strengths, but most of their units have critical weaknesses that you don't really understand the true severity of until your regular opponents catch on and hammer them time and time and time again.
Tomb Guard are probably among the best examples. The Banner of the Undying Legion looks like a really cool tool for them, as you and Sunny pointed out, allowing them to be outside the buff bubble laying down some hurt. Sadly...it's a trap. S5 is just plain not good enough without the extra little kick of AP, and something like mournfang or a demon prince get into the unit and just grind all 500 points of them into dust over a couple rounds. Without buff support very little in the TK arsenal can go toe-to-toe with the enemy. TG are simply too expensive, and too fragile, to risk in this manner. They are much better used as a points-denial tool, to protect a gunline or anchor your centre. Pretty much like Grave Guard for instance.
Some other points:
1) The attack I was referring to on the Warsphinx is its "thunder
crush" attack, being the one it can trade its regular attacks for to drop a stonethrower template into base contact. It hits against the highest WS in the unit, so is almost always hitting on a 4+...which is why most TK players will rarely, if ever, risk it (you only want to do it against infantry, and missing is often enough to have the warsphinx pop on SCR). However with rerolls to hit it's suddenly a lot more powerful, and rerolls to wound...well...you're going to wreck some infantry something fierce.
I should also point out here that the warsphinx is basically unarmoured. Thus you really need to be careful about what you throw it into. T8 is great until your opponent starts rolling a whack of 6s. Anything with high attack volume is your nemesis here. You're looking for elite units with high S that are wasted against the T8. Or to be close enough to a LoV caster to heal its wounds off.
2) Should be mentioned that the casket is T10 against shooting. It's actually really resistent against warmachine fire, which makes it good for target saturation. In a magic-heavy build I usually like having two for redundancy, given how important that +d3 dice is. Plus having the threat of Light of Death twice in a phase is pretty awesome. Note that the second casting can't target the same unit (including units it bounced to). In my reading this includes if the original casting was dispelled.
3) I don't think the Banner of the Undying Legion deserves to be green. A T4, 2W herald with only a 5+ save is too fragile to have much utility, especially when another level 4 caster is nearing the same cost.
4) Skullapults: keep in mind that there are lots of things that are immune to flaming and/or magical attacks. WoC demon princes chief among them. Make sure that if you're relying on these things to take out key targets, that you have a backup in case that doesn't work out.