From what I can gather...I would think that if you selected your text fonts (just the text that is jagged, are they all one color, like black?) if they are then this should work, using the magic wand, Select using All Opaque,
Now depending on the size of your text use Top menu item:
Selections>Modify>Select selection borders. Give yourself a little bit of space on both sides of the text if possible. (This is hard to explain but it kind of is going to almost give you what would be a selected outline of your fonts) Clear as mud right?
Hopefully you only need to select a few of the inside black pixels and give yourself a couple pixels around the outside, because next we are going to use Gaussian Blur to just blur those jagged black pixels into a smoother transition.
Your gaussian blur setting will vary also depending on the size of your text, but I would guess something about 3-5 strength should do it.
Well play with that and let me know how it goes!