I had a Gev, Scaled Scorch on the board which includes the effect Ward - Pay 2 Life.

Ward is an effect that is defined as, "whenever an opponent targets a creature with ward, they must pay the ward cost in addition to the spell's casting cost."

My opponent cast Monstruous Rage on my own Gev, accepted the Ward pop-up, cast the spell on my Gev to grant it the +2 attack with trample, and ... didn't lose any life.

The effect of Ward is clear: ANY spell or effect is subject to the ward cost, not just spells that may intuitively be considered as beneficial. A buff may allow the opponent to cast a kill spell dependent on the creature's power, for example, or draw a card.

This is an obvious oversight and incongruent with the defined mechanics of ward.