As the title says. Would he make a good tank?

Yes, ever since the new patch where they let us reconfigure his skills (and every other party member) from the beginning this has never been an issue. Good armor and skill allocation, along with good hardy food before a fight, will make up for any perceived attribute point distributions. You honestly don't need to min-max with a tank, his or her job is just to hold the line - often by plugging up a doorway. 

Edited June 11, 201510 yr by Venatio

I found him to be a great tank even before you could reconfigure his skills.  I found making an uber tank, unless you are playing PotD (which I have no experience with and so cannot confirm nor deny effectiveness there) is actually not only unnecessary but actually a waste.  Eder can both tank and do decent damage if built right, with the emphasis changing depending on what weapon set you equip him with. 

I'm playing on PotD, first play-through, and Edér has made a fine tank thus far.

 

I'd say I'd definitely be able to complete it with him as tank, but haven't done so since I'm reading all the text.

Edited June 11, 201510 yr by s13ep

I'm with Flintlock on this.  Eder made a very good tank even before the ability to manage the Companions' talent, ability, and skill choices.

I've exclusively used the default companions in my playthrough thus far, and I wasn't able to respec Eder after v1.05 as he was already in my party, but he has been a stellar tank for my party thus far.

Unless you intentionally mess up a fighter's stats/talents/equipment, they will at least be decent.