Previously I had been trying out the Blessing of the Gods on my Stampede. This gave the unit Elite - re-roll "1"s to Hit. The unit is one of my heavy hitters, generally with +4 to wound on the charge, so my opponent's De is irrelevant. With 30 attacks hitting on 4+ the non-Elite Stampede will theoretically do 12.5 wounds versus any opponent. With Blessing of the Gods this increases to a theoretical 14.6 wounds. So for 25 points I am increasing my "typical" damage output by 2.1 wounds.
Obviously the critical thing is that this is a one use only item.
From my point of view the new item looks really promising. When you move to a theoretical 17.0 wounds compared to 12.5 (no Elite) or 14.6 (Elite) you open up all sorts of battlefield possibilities. There are very few units in the game that could reliably survive a 17 + 2D6 Nerve Roll. This allows you to throw the Stampede at virtually anything with a high probability of blowing through it in a turn. It removes the need for a charge partner allowing you to commit the supporting unit elsewhere.
Yes, it is only for a single round of combat but if used correctly it can change the nature of the game very quickly. And in turns where it is not used the unit is hardly a slouch. I think of it as eating a mushroom in Super Mario!
There is a lot of analysis in KoW that looks purely at output in terms of wounds inflicted per point paid. That is fair. However in this case I think there is a tendency to miss the wood for the trees. By amping up a unit like the Stampede for even one turn you turn it into a different beast in terms of battlefield capability.
For 15 points this is a very good investment IMO.