RE: Gold Card Reward: Good or Bad?

It's a rare card so you would need a lvl3 summoner to use it. As you say it's used in a big mana battles. That's 5 x Malric Inferno's.

These are going to be more frequent after the end of season as the mana cap will be extended to 38 at times.

I use this card occasionally, it's better when it gets the second tier ability (Lvl5) of thorns.