if given an activation cost, the card cost should decrease as a result as well, as it loses the surprise factor that it had going for it.
I don't know if cost reduction is warranted with activation cost.
This creature has quite reasonable stat to cost ratio already. I actually think its a bit OP right now, personally. Given that its ability would be potent, even without the OTK potential, I would need some cost theory to justify reducing the cost.
The +2 ATK gives
a lot of new flexibility that it currently lacks.
Combo-ing this with scorpions of any variety is very potent... same goes for vampires... or immaterial creatures. Dive is another potential option. Its not just limited to fractal spam tactics.
Moreover, while the activation cost limits the surprise factor, it compensates by making the timing easier to pull off.
Right now, to get multiple orks to trigger, you have to cast them all on the same turn... that is very expensive.
With an activated variant, you can cast them on successive turns, then activate them all at the same time. This has the added advantage of meaning that multiple activations will require less hand space as well... so now you could very reasonablly pull of a fractal-spark 'otk' by amassing sufficient number of orks then blitzing all at once.
It does indeed change the feel of the card somewhat, transforming it into more of a long term stall (or stall breaker) rather than a sudden death. But I think that may be a good thing.
Lastly, the vampire combo could be pulled off as a "surprise" attack (e.g. opponent does not know what is coming until it happens) by using cloak. The orks would hide and amass under the cloak, then activate all at once when you play a full hand of vampires.
Even with 4 vampires and 4 orcs, thats a very potent combo...
The 4 vampires would end up being 18|4 's (or 14|4 if the buff is dropped from 3 to 2)... that's huge. You would heal more than half your max HPs in a single turn and it would take a double firestorm for your opponent to effectively to deal with it.