Harrison has major card draw potential and a much bigger body, so it's not in the same league. And as has been said, if you nerf Ooze, it only makes Harrison more powerful and necessary. That's poor design.
It's not a big tempo card. It's meant to reverse the giant tempo swing a weapon can bring, ie: two minions for the price of one card. By itself, it doesn't give a lot.
It's only "good value" against certain enemies, and even then it has a secondary pre-requisite that they have a weapon in hand as well. When an ability needs that many planets to align, it should powerful to offset how situational it is.
And, again, most weapons will have already replaced themselves in value by the time an Ooze is used anyway. If they haven't been used, well, that's the empty-board weapon gambit.
If it was 4cc, it wouldn't counter the early weapons as well.
Plus, it's not countering a full 5cc card by the time it drops. 95% of the time, the weapon will have been used already, so its already got about half its value and one-for-oned. If anything, it's a 2CC countering maybe a 2.5cc etc.
Also, by the same token, a 3 mana Hex counters a 9 mana Malygos etc.. That's just the necessary nature of counter cards. If all counters were the same cost as what they're countering, then there'd be zero risk to playing the initial big cards -- because, at worst, they'd spend just as much to get rid of it as you did casting it, so there's no real risk involved.
And I've already argued (quite well, IMO
) why it's not as valuable as a Black Knight: TBK is much stronger and tougher, plus it kills something that won't have already used up part of its value, like a weapon likely will have.
