The best global buff in Heroes vs Hordes is the 5% increase in the gold key chance from Santa's forge. Gold key chance increases are incredibly rare to find across the game.
The best global buff for damage and progress is the 2.5% cooldown buffs from heroes like Barbarian.
I missed the Necromancer when he was the adventure hero. I now have 300 shards for him, but I can't use them. His 2.5% global cooldown buff at level 100 would have been fantastic.
