This would be a bit of a PitA, but... you could add a dummy parameter to each link, on the order of zz=1 and zz=2, etc. For each email, you give each link you want to track a unique number, then you set up 5 campaigns for "contains zz=1" and "contains zz=2" etc.
The parameter isn't doing anything except triggering the specific campaign.
And also, I'm fairly new to Marketo, so am not positive this would work, but I think it should.
And come to think of it, you could come up with a paradigm for what 1, 2, 3, etc. means (or use more obvious names than numbers, but I like to be obscure). So links to "Buy Now" are always tagged with zz=3. That way if someone hits on the zz=3 campaign, you can record that as "clicked on Buy Now link." And since you're scoring on this, you might want to score that higher than "clicked on Feature Article link," right?