Has the idea of causing a creature's attack to be redirected randomly been done before or have potential? Should it be a spell (one use, perhaps last more than 1 turn and cause confuse status), permanent (must cast each turn) or creature? If confuse is a % chance to attack something random, what should it be?
I am sure there have been creatures that attack randomly and I think there have been cards to make creatures attack randomly.
Let's count randomly redirecting as twice as powerful as blocking for the purposes of outlining the thought process below.
If we were to block a single creature for 2 turns (random for 1 turn),
Would it be a spell? No. The effect is to small for a spell. Freeze gets 3 turns of blocking and preventing skills. So a spell would require at least 4 turns probably 6 before being useful in card form.
If we were to block creatures for 2 turns (random for 1 turn),
Would it be an AoE spell? Perhaps. It would act similar to a 2 turn Dimensional Shield that does not use the shield slot.
If we were to block creatures for 2 turns (random for 1 turn),
Would it be a permanent/shield? [I know of a recent shield that redirects to the opponent 25% of the time]
This would be similar to Procrastination.
If we were to block a single creature for 2 turns (random for 1 turn),
Would it be a creature activated ability? Possibly. Guard delays for 1 turn with a drawback.
So a multi turn single target spell, an AoE spell, a shield [already done] or a activated ability depending on the shape you want the influence of the effect to have.
The chance is the easiest to tweak variable. It depends on the rest of the card.