I would definitely disagree with respect to the 04 age group. Did DA take a bulk of talent? Yes, but ECNL, not even close, at least for the 04 age group. Haven't seen Slammers or Arsenal, but based on the standings, it looks like Arsenal lost most of their talent. I have seen all of the rest and all but Strikers, I would classify as in the very good range and on par with the better flight 1, CSL, and DPL teams. Strikers would be an underdog against the better teams from these other leagues.
This is how I saw the 04 age group prior to DA. You had about 6 elite teams, followed by about 7 or 8 excellent teams, then anywhere from 20-30 very good teams. The difference within each group is slight. The breakdown is probably similar this year. It looks like 5 DA teams have elite talent. Then there are the next level teams (6 from DA), followed by plenty of evenly matched very good teams. Maybe the top team in SCDSL, CSL, ECNL, & DPL is close to "excellent," but most of the top teams in these leagues would fall in the "very good" category for me. The difference between these "very good" teams from different leagues is not much. That's why I would not agree that ECNL has more of the "bulk" of talent than these other leagues.