This would be so broken, champs would just spot them on for asura then swap back to dl sleips. No suport, some cards are not meant to be mass distributed.
If a card isn't meant for mass distribution it isn't meant to be in the game at all.
Note, these numbers do not count any cards used in head gears to further increase asura damage and are just rough numbers.
Over the current top tier gear, you would get this kind of boost in asura with this card. You decide what is appropriate.
50% gives a 38.9 % boost
40% gives a 30.7% boost
30% gives a 22.5% boost
20% gives a 14.4% boost
There is also the possibility that this could be made more of a team oriented card. The card would have a higher SP boost for champs then would normally be aloud however, it prevents you from getting IC. You would just need to pick how long you want that cast time to be and adjust the card accordingly. A champ would need help from team mates to use asura strike with this card.