MMH5.5 - Heroes of Might and Magic 5.5

Just did a quick test. Armorer decreases magic damage by 15%, combined with Forge Master, you get roughly ~33%. Not sure why it doesn't cut it at 35% as it should.

85% * 80% = 68% (32%)

If "Armored spikes" give +4 at once, it will be way too big of a buff for the early game. Frankly, I don't think it matters much even if it did work the way you are proposing because the skill points in MMH5 benefit the player way less than in ToTe.

I invest two whole level-ups into these +2/+2 (one - to increase the useless passive skill by +7.5% retaliatory damage). I can definitely say that in its current form, I will never invest in +1/+1 before level 20 (when the bonus becomes +2/+2). That is, if I was still unsure whether the Hyrdas would pay off, here there are no doubts - the perk is useless for its cost (2 level-ups) until level 20.
I highly doubt that a +2/+2 bonus can break anything in the early game. And it's not +4, but specifically +2/+2 (which is usually weaker).
On the other hand, there is an alternative in the form of x1.5 damage, which definitely combines with the Avenger's Strike, and therefore is more appealing, and after that - take Support. And all this is clearly more attractive than some +1/+1.