Balance is not "every unit is exactly the same" and it shouldn't be. Nor is it even every unit is good. That is a pipe dream, it doesn't happen. Not in table top games, card games, role playing games not in any other game where players make choices. If you want that type of balance play checkers.
Balance is that a variety of armies can compete. And they can. At all levels. This has been proven. And yes, in the hands of generals of the same calibur, a highly competitive list will beat a non-competitive one, but again, that happens in every game, it is not unique to table top wargames or to 40k in particular.
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If he would like to discuss his local meta and the competitiveness or lack there of, then that should be in its own thread. This thread is specifically discussing 40k at LVO, which was a healthy environment. Even if we widen the topic to tournaments in general, the data we have supports a diverse meta at the top of the charts, not 1 or 2 armies (or 4) destroying everyone else.