dang, now I gotta buy PHB2.
I don't know about the other one, but Karmic strike gives you a -4 AC, instead of increasing the enemy's attack by 4.
as another tactic, instead of getting rid of the minuses from the feat, for my character I made them worse (took a level of barbarian to get the extra damage from rage, giving -2 AC, and took Reckless Offense which gave me -4 AC +4 attack, or damage, I can't remember which)
I had 0 AC. But it was fun
I got the zero on purposely, didn't wear any armor or anything (with rage and scout I couldn't have gottten anything good anyway. It was worth it for the fun in responding when the GM asked "does a one hit?". I had a GM who laughed alot that time, so it was funny.)
If your going to have a low AC anyway, you might as well concentrate on other areas. The potential for Karmic Strike is the same as for two weapon fighting (which, by the way, karmic strike vs. a two weapon fighter would be fun), damage multiplies fast with alot of hits.
I had monkey grips, Extra Rage (+2 rages/day) , Instantaneous Rage, and 1 level of scout. plus a few levels of fighter, unfortunately I was too low to get any really cool combinations of other feats (those and one or two others were all I got, I was only sixth level)
I had another character (this one won't be as long a description) that used Karmic Strike, he was a Tactical Soldier (prestige class from Miniatures Handbook, my favorite ability from it was the one that allowed me to take a blow for an ally, so he wouldn't have to get hurt) which combined well with Karmic Strike ("oh no, the Ogre is about to kill the Kensai!" /switch places/ "Die Ogre, Die!"). He could really take a hit too.
though there were some rules questions about that character.
/power gaming over
My Answer: I have always felt that Karmic Strike was the coolest feat of all, I've never gotten it to work right. For me, the only Karmic Strike tactic has always been increased hit points. Since this new one gives the enemy more damage, I would have it say it's worse (for my tactic), but I would have to see the true wording from the PHB2 before I came to consider that a final decision.