Dirk is a great player. A first-ballot Hall-of-Famer, all-time great at his position.
That said, there is absolutely no metric by which Dirk could compare to Lebron and Durant this season. Both Lebron and Durant him surpass him statistically almost across the board (both by the box score and by the advanced metrics like PER, Win Shares, Wins Produced, RPM, etc.). They are also both far superior to Dirk at defense than Dirk was at any point in his career.
Even Dirk's best season:
26.6ppg / 9.0rpg / 2.8apg / 1 block pg / 0.7 steals pg; all on 50/40/90 shooting
Doesn't surpass Durant last season:
28.1ppg/ 7.4rpg / 4.6apg / 1.3 block pg / 1.4 steals pg; also on 50/40/90 shooting
Or Lebron:
26.8ppg/ 8.0rpg / 7.3apg / 0.9 block pg / 1.7 steals pg; on 56/40/75 shooting
So, no, unless you are judging in terms of "best hair" or "best accent" or "plays for Mark Cuban," there is no comparison you can make by which you can say Dirk is better than Durant or Lebron. In his prime he was comparable, but not at this point in his career.
Now, LaMarcus is having a wonderful season by most standards:
23.2ppg / 11.1rpg / 2.6apg / 1 block pg / 0.9 steals pg; on 46/20/82 shooting
Which is on par with Dirk's season (rebounding better, but significantly less efficient at scoring; worth noting that LaMarcus played about 5 more minutes per game than Dirk as well)
21.7ppg / 6.2rpg / 2.7apg / 0.6 block pg / 0.9 steals pg; on 49/40/89 shooting
But is notably lower than Durant or Lebron.
So, to answer your question, it is too early. LaMarcus is 28 and in his prime is having a season that is roughly on par (maybe better) than Dirk's season at age 35, years removed from his prime. Career-wise, he seems to be a poor man's Dirk Nowitzki. There's no shame in that, it is a phenomenal accomplishment for a basketball player. And he has a lot of career left to prove otherwise, for better or for worse.
And that still puts him a step behind Lebron and Durant.
Sorry to break it to you
EDIT1: Just realized I brain farted and used Lebron and Durant's averages from LAST season for some reason. I didn't mean to do that, just distracted watching the playoffs I guess. Anyway, I'm too lazy to go back and change it, but it doesn't change anything. They are having almost identical (in Durant's case better) seasons.
EDIT2: With regards to LaMarcus' two 40+ point playoff games, that is a great accomplishment. I'm happy for him. But two games does not a Hall-of-Fame case make. Antwan Jamison, Jamal Crawford, Corey Brewer, and Brandon Jennings have all had 50 point games in recent memory.