Wow, great to see these at last!
Hoping there'll be some files through which we can all print these cards at home, to complete our collections!
Veteran Crusader is interesting: 0/3/3 non-loyal ambushing is very solid already. Putting aside the ability for now, what we may be looking at hear for Mavros is 5 attack that can be ambushed in for 2 resources. Of course "enters play" is a more open condition than "deployed", which helps for DPA and Black Templar shenanigans.
The ability looks to be benefit/harm neutral, but of course its not, as the deploying player controls its timing. Actually, its a very powerful kill effect, which the deploying player can plan and play around. Set a trap by stacking two cappers on a blue planet, wait for the opponent's warlord to commit and kill a capper, then ambush in this unit.
All in all, I'd say with context in mind, this card is almost as good as Klaivex Warleader, and probably undercosted by 1R.
My main criticism of this card, however, is that it makes a swingy game swingier. Opponent has a Heldrake or other enormous elite alone on a planet? The 2 resources effect triggered here will either leave it unscathed, or kill it outright, depending on your opponent's ability to read your poker face, which is basically a 50-50 coinflip. A cheap effect that has a purely random chance of flipping the game, that's not my idea of fun. Yes, there are counterplays, like not playing the elite till you got a disposable army unit there, but largely its another swing play in a game that ended its play-life in a place where the effect of luck was already on the rise.
Herald of the Waagh is just perfect. 4 for 1/2/3, with the Warrior trait for Straken. It's a little bit expensive feeling for something that needs specific circumstances to be useful, but on that occasion that those circumstances collide, it's great value. Use it to kill a command unit before the command phase, and claim command there and a battle ability as an added benefit.
Obscure uses abound too: Use it to clear Tyranid infestation with irritating timing. Use it to get under Slaanesh's Temptation.
All in all, I think this is my favourite card. Not an autoinclude x3, but a definite consideration for splashing 1-2 copies out of any Ork warlord, and probably into Straken and Zarathur too.
War Father's Shadows again feels a little overpowered. The base of comparison here looks to be Honored Librarian, but I'd say Ambush is at least as good as Librarian's ability, and the resource thing is a bonus on top of that. While 4 cost might have been too high, I think this card could have cost the same and gone down to 1HP, which would balance all that aggression with fragility.
War Father Nathaniel is appropriately costed for its stats and ability, and is a nice new design space. Could be interesting out of Tau decks, as it could then benefit from Tau discounting and general ranged synergies, as well as having the subtle effect of encouraging an opponent to commit to resource planets, leaving a likelihood of higher card draw for the card-hungry Tau deck. I like this a lot, with my only complaint being that resource choke feels like it shouldn't be an SM mechanic.