The game needs to limit the rate of growth. They say:
What is the maximum amount of growth possible: G
What is the least amount of time we want them to spend to get it: T
What is the rate of growth: G/T.
They can limit rate of growth in many ways. One obvious way is to put a hard cap on how many times we can go per week, or how much 'tomes' we can make per week. The other is how many hours of repetition (i.e., RNG/Grind) does it take to obtain a specific amount of growth.

We can choose our limiter. The amount of hours we sink, or the amount of 'tomes/repeats' we are allowed to do. In other words: Would you rather be limited to 1 Coil Run per week, or be allowed to do 100/week but the drop rate decreased to 1% of its present drop rate?
Because being able to do it more often per week with the same drop rate is not an option. Perhaps when iLvl150 gear is out they may remove the restriction on Coil (as it will be a moot point anyways).

But honestly, the issue is NOT the loot lock out, the issue is NOT the caps/growth limits. The issue is one of the main areas of interest in the game is accumulation of equipment. This is a self-defeating goal. There needs to be other key areas of interest in the game that we would all enjoy spending time doing.