Bloodreaper and Holy Avenger add a lot of flavor and strategy to the Warlock and Priest; however, I see some problems with the viability of these abilities given each mage's limited or non-existant access to level 2 creatures.
In the case of the Warlock, I'm finding it difficult to actually use Bloodreaper for 2 main reasons; no level 2 demon to round out the retinue of demons, and the fact that Dragonscale Hauberk, a very popular equipment, completely defeats 2 out of the 3 demons available to be Bloodreapers. This leaves the Dark Pact Slayer, which is a very good creature to be sure, but given the Warlock's naturally lower channeling, is not always a reasonable choice. I don't feel that Warlock players should be pigeon-holed into playing a Dark Pact Slayer every game, nor do I feel that they should be required to look outside the Dark/Fire schools for a Living level 2 creature.
I would like to see some kind of level 2 demon, and preferably one that does not deal Flame damage. The Warlock's weakness to Flame resistance is so pronounced that I don't think another demon with a Flame attack is really necessary.
For the Priest, I understand that there is technically a level 2 Holy creature available, the Asyran Defender, but I think it needs to be officially made tournament legal so that people don't feel discouraged to play with it. This is less of an issue, since Priest players have a larger card-pool of potential Holy Avengers, but nearly all of them are relatively expensive level 3 creatures.
I think this is important concern for the balance of the game, because other mages are not limited like the Warlock and Priest are. The Beastmaster and Warlord, the two other mages with Pet (or pet-like) abilities have lots of creatures to choose from in the level 1, 2, 3 and even 4 range, and thus don't struggle at all to find the proper pet or just creature for a given situation. Furthermore, the Forcemaster, Wizard, Johktari Beastmaster, and Priestess all have abilities that do not rely so heavily on their cardpool to actually make use of their abilities.
Hopefully there are level 2 creatures in the works, so that these abilities can be more flexible. Thanks!