you are largely correct, i will quote myself from srk:
the frame data on ex mgu is VERY misleading. The strike invincibility (5-31f) applies only to his head.
Right now its extremely poor as a reversal because it only has 1-4f full invincibility despite 12f startup (unless, like i said, you are aiming for his head), so what usually happens is either:
1. The move you throw out is active during that 8f gap and EX mgu gets stuffed completely (usually what happens with mid-striking meaties that have a lot of active frames like ryu c.mp, makoto c.mk, both of which make all upkicks whiff as well)
2. The move you throw out intersects with EX MGU's invibility frames, and because of the slow startup the move recovers before ex mgu reaches it's first active frame (i.e a meaty c.lk from most characters)
Now originally when DWU and the EX MGU buff (6f startup) were announced it seemed promising. It's still not fully invincible until startup, but the gap is much smaller (a 2f gap instead of 8f gap) so it would trade with (but not beat) meaties more, which is good.
However, Capcom secretly nerfed the invincibility frames on it (notice that Combofiend didn't mention it in his vid) so the invincibility is only 2f now. What this means is there is less of a chance for whatever meaty you stick out to intersect with the inv frames of ex mgu. That is why you saw things like Gief beating DeeJay's EX MGU with a jab. You can stuff the move with buttons that don't need as much active frames as before. So essentially EX MGU's viability as a reversal hasn't really changed at all, but now we have more recovery on it.
Basically as a wakeup it winds up being more or less the same. On the opponent's part they is a risk of trading with ex mgu (not really a risk of it being beaten clean unless the normal doesn't have a whole lot of active frames and it ends before the 2f of EX MGU's full invincibility ends). However, at the same time, there is also a greater chance of stuffing it because there are less invincibility frames to deal with (and essentially "eat up" your move's active frames). It's kinda weird to explain, as im saying its both easier and harder to stuff the move. Basically, its a bit better against poorly timed shorts, but worse against strongs and fierces. The normals that DeeJay had the most trouble with in matches (normals similar to Ryu's low strong), are pretty much completely unaffected by this change, or delayed wakeup in general. You just wait until deejay starts to get up and you hit the button. It stuffed everything deejay can throw out before, it will stay the same now.
In terms of throw invincibility he already has that in all of his upkicks, and mk, hk, and ex sobat if he has charge (it was a property in lk sobat but they stealth nerfed it, similar to what they did now).
You then have positives like adjusting your wakeup now, and negatives like increased recovery, the risk-reward of the move, and it's viability as a reversal stays essentially the same. The changes of EX MGU actually benefit it's viability in combos more than anything, with the quicker startup, an increased hitbox on the first hit to prevent whiffing during combos, and a higher launch to make followups like dash ultra easier). I don't really think that it was that bad of a tweak, and the change doesn't hurt DeeJay, but calling it DeeJay's "savior" in a wakeup is very disingenuous and is preying on lack of character knowledge in favor of "hype".
well at least on the plus side i have been experimenting with some stun resets with RFA on Akuma haha. They are pretty ghetto but i'll put some vids up in a bit.
*edit2*
Some quick playing around:
http://youtu.be/nk1YO_XkHZc