It’s just my personal opinion, but this doesn’t bother me. LGF itself is immensely powerful, even far below 30 stacks. At 10 stacks (aligning with base 10sec CD) that’s a 4000% multiplier on a 620% base skill, which is more than powerful enough even compared to other classes’ leveling multipliers. In fact, 30 stacks is almost certainly Overkill (or 15stacks with Pinpoint Accuracy’s 15second, 1600% damage).
My biggest gripe with it, for leveling, is that it’s a close-quarter, small range attack on a sizeable 10 second CD. It’s just fairly clunky and dangerous for leveling. It’s the most useful tool we have, by a mile, but it’s not a great one.
I don’t expect Blizzard to make any changes to base skills at this point in the game’s cycle. The skill’s design and numbers are likely as set in stone as they’ll ever be. Unfortunate, but realistic. 
However, changing an item’s required level is absolutely trivial. And while it’s not an ideal solution, it would be a very useful and powerful one.
Please,
Reduce the level requirement of The Ninth Cirri Satchel