Rules Question - Power from Pain - Fearless

Dave and I played a 2K battle yesterday and something interesting cropped up. I've been testing out webway portal lists with my Dark Eldar with a fair deal of success. I'm hopefully going to take them to Blog Wars 3 once I've had a bit more practice and got them all painted up. Anyway, my wyches were cutting into Dave's Tau (well mine that he was using) and one wych squad had managed to gain two pain tokens. However, the sheer weight of Tau shooting severly dwindled their numbers and eventually they fell below 50%, failed a morale test and started running.

All pretty normal so far. Anyway, a nearby Cronos (which are awesome by the way - more on them later) opened up with it's spirit probe (AP3 flamer) and killed a nearby Tau unit. This generates a Pain Token and I thought "can I give this to those wyches to make them Fearless?". After a brief discussion we decided that since they were now Fearless they were no longer running and could immediately regroup.

Do you agree with this? I personally think it isn't unreasonable. If the wyches had greater numbers and were shooting at a unit as they fell back they could potentially kill it and gain themselves a pain token making them Fearless (assuming they had 2 already).

The question is, does it instantly regroup them? Does it regroup them at all? I mean this is obviously assuming that there are no enemies within 6". I checked out the GW FAQ but of course this was no help at all and I can't find a discussion about it on the net so I thought I'd post it up. The only other example I can think of is when a unit of craftworld Eldar is falling back and comes into range of an avatar which automatically regroups them. To quote the Eldar FAQ:

"Q. If an Eldar unit finishes its fall back move within 12" of a friendly Avatar (or he moves within 12" of a unit that is falling back), does the unit immediately regroup?

A. Yes, the unit immediately regroups, just like a unit that is assaulted when falling back (this means that it ignores regrouping restrictions and it does not move the usual 3”). Also note that regrouping as described above is the only thing that the unit can do in that phase."

It's a very similar circumstance. In my opinion the unit gets to immediately regroup and therefore will act as normal next turn (assuming it doesn't get broken again in the enemy's turn). I think, considering how ridiculous the rules are with Space Marine regrouping this just goes some way to helping the xenos out! Let's face it it's a pretty rare scenario.

What do people think? Should we have played it differently?