Okay, for reference here is what I play at and what I see.
I have a 23" big, 1920x1200 pixel monitor, although I play windowed so the screen is slightly smaller.
edit: Apparently the image is too big, find it at the end of the post please.
and a small and large tooltip for my train of thought:
Okay, from the top:
Name: Well, this deserves it's own line I think.
Economic Line: Maybe this does not need to be the first line in the tool tip, but only one line of economic info is as small as you are going to get.
1st White: Attack information, again only one line. Maybe this could be color coded red somehow?
2nd white: Ship information, including defense. One line again. Could be color coded? Mind you, with only 2 white lines it's not like the info is hard to find.
Green Attack Multipliers: One line, but worth it, this is important.
Light gray Abilities: These need to be listed, perhaps the most important information for me.
Dark Gray immunities: Again, very important, I want these listed.
Yellow AIP: Critical, needs to stay.
Blue Description: This can go, no gameplay affects here, once you've read it once you don't need to see it every mouseover.
Now, icons vs. text. I'm not sure how I feel here. One of the biggest reasons icons are used to replace text in other games is the control bar along the bottom of the screen is always up and so it blocks game play space. Because the tooltip is pop-up, that is not a (or as much) of a problem for AI War.
Looking at the tool-tip, I actually don't see much I would want to change.
The biggest thing I can think of is that screen space for smaller resolutions. Maybe a control could be added to hide tool tips, then a show/hide tooltips key could be bound.
So if 'hide tool tips' is unchecked (current behavior), the 'show/hide tooltips' would hide the tooltip so you could use that part of the screen.
If 'hide tool tips' is checked, the tool tip would never show until you pressed the 'show/hide tooltips' key.
But if I actually had to cut down the size of the tool tip, I would get rid of the economic stuff and move the Ship Cap up to the right side of the same line as the ship name.
I'd then combine the 2 white lines into 1, only keeping the health, attack power, range and reload.
That would get rid of two lines, but I can't see getting rid of anything else.
This all assumes their would be a 'full details' button that would show the current tool tip.
D.