The expansion is named Druid vs. Necromancer or Life vs. Death. I hope I am drawing a big circle around this point. I would be greatly disappointed if the Druid was excellent at fighting the Forcemaster at least from a "mechanics" point of view.
I get the theme. I just think there are subtler ways of balancing than a simple bonus vs. the opponent in that set. Should they design a card to be simply a Silver Bullet against one particular opponen?. It's far too narrow a benefit. Surely cards need to be designed for interactions with all current cards? I am very impressed with many aspects of this set previewed so far, just +2 vs. undead feels like lazy design. Sorry.
For example. zombies have resilient and lumbering. They have already added Acid Ball as a level 1 water spell to bypass resilience whilst also solving the meta issues like Golems. They gave the Druid (only) the "I can sprout my vines anywhere" mechanic to exploit lumbering (then balanced it with Rooted). These are mechanics that also interact with other mages. That's why I complimented the design team so profusely as I was really impressed by the interactions, the thought that has gone into them and how they completely shake up the meta.
I appreciate there is the Strategy-Focused vs. Opponent-Toolbox axis of the game. I don't have any issue with promoting a reactive toolbox strategy. So now my Beastmaster has Galador vs. metal/incorporeal and Kralathor vs. undead. So, after thinking about it more, this is only 1 Epic card which cites "undead". I think having a few such cards is probably good for the game in opening Toolbox book strategies more.
After considering this more, I retract my initial concern (+2 bonus does seem thematically forced, they even added flavour text to explain it) in the fervent hope there will be only Epic creatures that are +2 vs. undead. Else it is a far too unsubtle direct mechanic for balancing. A bit of toolbox (Epic so can't be spammed) is good for the game. Anything that adds more variety (hence surprise) to our spell books is good.
What is surprising a bit to me, is that Holy gains very little here. Light doesn't have any uplift (Light +2 etc.) and healing doesn't cause damage. So for the Priest/Priestess going out to battle the Undead, have only the Staff of Asyra, Blinding Light, Pillar of Light, and the Angel of Light get nonliving buffs....no love on that front at all (so far, fingers crossed).
You forgot Temple of Light (still viable, especially as toolbox vs. undead). Light hurting non-living more (+2 or just +1 if also hurts all Dark) partly makes perfect sense thematically (vs. undead) but also for balance (vs. constructs, elementals). They could have made Light more powerful against a narrower category (+3 vs. undead) but that would make it too much of a Silver Bullet which I don't feel comfortable with in a game of "pick your spell". I think they pitched Light right between the range of what it benefits (more than thematically makes sense) and the bonus Light gains. Also, the very fact there will soon be far more non-living creatures in the game benefits Holy mages indirectly.
A rule "Healing instead deals damage to Undead" is neat (very D&D) but does not work consistently with current card text. Minor Heal and Heal will hurt them but Group Heal, Asryan Cleric, Healing Charm, Vampirism and Regrowth won't (those enchantments can't target them else you will have the ability to use Regrowth like Ghoul Rot for undead). Such inconsistency jars with me. I would far prefer a consistent approach. Also, where would you add this? Undead is a subtype, not a keyword. When there are more important intuitive issues to solve (plants cannot be doused when burning, area poison effects do not damage plant conjurations), both of which I hope they do solve, I don't see the value in adding this Heal vs. Undead rule. It's a neat idea though, and would add to the versatility of unloved active healing spells.
If Altar of Peace (a total game changer for any control mage build) and Temple High Guard are in the set, would that make you happy?