No one is a big deal in TNA. Every one not in the X-Division is completely interchangeable. Angle stopped being a big deal after two months, Jeff Hardy stopped being a big deal on the night he debuted. There is no one in TNA that comes out and it's like "Oh man, shit is about to get real". No one. Everyone is at the same level. TNA is a complete aura killer.
Things have gotten better.. You bring up some good points but since Russo has been shown the door TNA has built up Storm, Roode, Aries and Joseph Park very well. They have made Joe credible again and let Bully Ray become the best heel in years. Daniels Appletini drinking metrosexual gimmick is fantastic and they even made Hogan tolerable as a GM. Dave Lagana has done a fantastic job overall even though the Claire angle was awful and the Aces and Eights angle is running out of steam. The roster has more believable depth than it ever has.
If Aries faced Ray tonight and Ray won the championship it would not be a reach, same for a number of other guys. When Sheamus or Cena are facing people we already know there is no way they will lose, especially clean. The only thing WWE has had over TNA over the last few months is atmosphere and production values, which admittedly are very important.
As for developing roster depth and pushing the midcard TNA absolutely destroys the WWE and has for a while. It sucks the ratings arent reflecting that, people would rather have cool PPV theme songs and shitty b list celebrities than properly developed matches and feuds.
TNA is far from great but overall has done a much better job AS OF LATE in developing their talent.