The people who are still TR'ing aren't keeping this game afloat... apparently TR'ing as an "end game" is worth about 20% more player activity loss per year than a game that has no TR'ing such as LOTRO.
TR'ing might have been a great thing for people who don't have friends or don't mind being in different level ranges from their friends for long stretches of time, (or amazingly can coordinate times to play together) TR'ing might have helped prolong old content in DDO massively... but TR'ing it is safe to say; is not enough of an end game to keep players around. That is clear from both Developer first hand accounts (that got said developer fired) and the only scientific metric we have available to us, as the data shows that when we HAD a wide end game with 9 or 10 Raids and 20 or 30 S/S/S quests, the player base actually INCREASED OVER TIME... where as; two months after they started to obsolete this end game (MOTU) with a cap increase, the game suffered a massive loss of players and a steep attrition rate for the last 3 years.
You can discount the Data, you can Discount the words of a Developer, but if you discount both you're simply playing the Ostrich.