Which cards? The two resource humans.

So moving on to the two resource cards for the humans we have four contenders... I'll talk about them with my own experiences.

Blake

2R/3D/1H

So Blake is a very decent dmg dealing card right off the bat if you can get him down turn 2, but I find his uses limited due to his 1HP... it means cards like Kris could come out in their own turn and kill him before he even gets to strike. Although if he does get going the damage can begin stacking quickly and if you get an Aeon and Birgitte out for protector and a few Blakes due to cheapness you can begin getting some serious damage out while giving them a few layers of protection.

Add in cards like war banner or Aldon again and you can see them doing 4-5 damage a turn... even doing that twice is a third or more of most hero's health, but as mentioned his HP really makes him straight forward enough to remove form play.

Puwen

2R/2D/3H

This seems to be a staple in most human decks, the ok dmg combined with 3 HP means Puwen cannot be easily one shotted early on by enemy allies and is capable of beginning board control. I've found 4 of these very handy in my deck for part of my T1-2-3 draws where i hope to get a kris out, then a Puwen to begin giving more support and turn 3 if possible an Aldon to really begin getting some good dam from allies. Making Puwen into a 3D/3H allies via war banner or Adlon is really handy for allowing you to remove some allies in one shot, or use the 3hp to soften it for kris to remove and thus keeping allies on your own board side.

What makes Puwen so desirable is the 3HP which helps him stay around longer while dishing out a respectable damage for T3 onwards

Dirk

2R/2D/2H - Ambush

A semi decent ally imo, his 2H makes him softer than Puwen, but his ability to attack with stealth stopping enemy return hits mean she can really soften up enemies for other allies to finish off, although with only 2HP early game allies like Puwen's or gargs for example can remove him in one shot. Thus making his uses a bit limited I've found.

Although as with the same tactic of Aldon or War banner he can begin offering some decent damage to help you soften up even bigger allies for the killing blow from elsewhere.

Katrin.

2R/0D/4H - (1) Targeted Ally gains 2HP, this ability cannot be used again while that ally is still in play.

I've never seen this card played bar in one game, and to be honest I didn't give them the chance to begin buffing an ally. Although i do see how her ability could be useful to buff another ally (Maybe Puwen or even Blake early game to make them into a 2/5 or 3/3 respectively) to keep them alive longer, and with 4hp herself f your opponent wants to remove her to stop this buff being cast as they keep killing the buffed ally she could cause hassle. 

The lack of any dmg is a bit of a downfall, but that can be sorted via the traditional routes mentioned elsewhere to give her some minor damage to aid in removing some health, sadly though she will not find space in decks which want to keep trim.