Biggie,
With all due respect to the others, I disagree almost entirely.
Tiering up early is definitely a challenge, but it's not one you should shy away from. I reached Legend at level 68. I'm currently at level 76 and, aside from a different driver, I still use the same clubs you use.
Tiering up early makes you a better and smarter player. It will pay dividends when your level eventually catches up to your tier.
In answer to your original question; Does club precision decrease, (or does deviation increase) as you progress in tiers? - paraphrased.
No. I had the same question when moving from TM to Legend because it seemed like that's what was happening. The truth was I was hitting longer irons into faster greens in stronger winds. The clubs haven't changed, just the conditions.
I recommend joining Young Guns CC which is a CC specifically for low level - high tiered players. You will find great advice in the YGCC forum specifically tailored to your unique position.
Being a LL-HT player is difficult, and at times frustrating, but the pay off of knowing you're skill brought you there is something level 90 TPs will never understand.
Anyone who says it's the clubs that make the golfer, or anyone who says you can't compete with inferior clubs, has never tried.
Good luck Biggie. Stick with it. Learn your clubs completely before shelling out money for new ones. Changing clubs often is a straight path to an inconsistent game.
Hope to see you at YGCC.