By that line of reasoning, there would be no such thing as "too grindy" nor is it possible for there to be gating in any MMO.
Because, really, this is what your position entail.
We're talking about one of the most insane grind I have ever heard of. Even if it takes 3 merely weeks per reincarnation (which is fairly conservative), it'll still take over four months to get six past life feats. It is only after
those four months that the player will be able to complete the other existing grind like favor and tomes. Oh, ya, that's per character and, if the player decides that he needs other past life feats, he'll have to restart those grinds.
Additionally, you can't do anything but TR on that character. Sorry.
Then, those bonuses do add up and do result in a gating. What is an obstacle for a normal character is a joke to a character with +9 Spell Pen. The two players just can't play in the same content: while one will have a lot of problems, the other will find it's a cake walk which means that the TR'd character will need new, more challenging, content. That content will be gated by a certain number of reincarnations. If the DDO developers talked with their LOTRO neighbors, they should have a clue of how unpopular gating is.
To put it bluntly, I don't see this as being fun, ever; and I'm not talking on a personal level here.