What do you think about the level size?
I think the level size was fine. Although I wish the camera was a bit more zoomed out so I can see more of what's going on.
What do you think about the blood bar? (Too much initially, not enough received from bloodpacks? Etc?)
I think the blood bar is fine. Perhaps increase the about of blood per blood pack? I was more stuck on the fact that I couldn't distinguish between the walkable area and the boulders and trees etc. that blocked your path. I think that there needs to be a way higher contrast between the two.
What types of powerups would you like to see?
I'm not really sure but I can say that I had no idea what the potions were for and what they were doing.
What do you think of the movement of the horde?
I think the movement of the horde is fine.
What other stats would you like to see besides the score and time?
I would like to see the effects of the potions have a more visual representation. If the potions are meant to give you a speed boost or something then there can be a symbol of two little feet running or something.
Does the score help to increase the replayability of the game (different play styles)?
Yes, I think it does since focusing on getting a higher score is the bases of the game.
We are planning on making a permanent (between runs) max blood powerup - the blue vial (currently just replenishes blood). Does this sound interesting or fun?
Ah, so that was what the blue potion did, my bad. I think making a permanent power-up can be a reward for reaching a certain level. Congratulations you made it past level 20 here if your reward type thing. Then the player might wonder what power-up they will get after making it to level 30 and so on.
Overall, it was a fun game, great job!