Maybe the formula for extra fire damage could be 10 + [(number of fire and death shards)/3] fractions rounded down, with a minimum of 1.  This should provide some bonus damage but not make it ridiculous if you've stacked death shards (which are the only damage related shards that it is possible to stack heaps of by converting them with Death Worship).

I just saw this item today for the first time... I think they must be sneaking in some new stuff via XML while we're sleeping.  I also liked how this weapon had a quote on the description. 

P.S.  I don't think the weapon is OP'ed..  You got lucky and found a weapon that matched the shard types you had.  That won't happen every game.  Besides, it is fun to find OP'ed stuff from time to time.  Don't forget the other guys are finding OP'ed stuff too. 

To clarify... i'm not saying its OP. I'm saying that the damage is being calculated wrong. I have 10 death shards and 0 fire shards... it should do 70 fire damage. It is obviously doing 3-4 times as much damage as it should, so there is a bug somewhere.

I did have Evoker III and other spell damage bonuses, so maybe thats where the extra damage is coming from? I guess that might not be a "bug" but simply a side effect of how weapon effects work. 

Evoker III (75%) + Path of the Mage (50%) + Cloak of Stars (50%) = 175% spell damage.

70 * 2.75 =  192.5 damage. This sort of makes sense since I am seeing 150-300 damage but I have no idea why it is so variable.

It is okay but it can certainly be twisted.  I do think it should only be fire shards though.  Or maybe change the plus to every fire+death combination.  I think you could come up with some interesting weapons that have certain multiple shard combinations.