[Sammas]

This is not consistent with earlier behaviour. Previously, I have been able to have 2 archmages buff each other in one round, [opponent moves], then attack with archmages, and on [opponent move] they retained the additional defence.

Additionally, note that the 'downpour' debuff lasts for 3 opponent turns, not 2 as would be expected from your explanation.

And the stoneskin icon was present for the unit (on my screen) during the opponent's turn, yet the unit did not have +2 defence.