First off, welcome to BikeForums!
Next, the problem you are talking about is not a Deore thing. If adjusted properly Deore will shift just pretty much as well as anything else. I really don't think you will notice enough of a difference to justify XTR. If you do want to change and you aren't loaded I wouldn't recomend going above XT.
If you really want to upgrade I always recomend going wheels and tires first. That is where I always notice the biggest difference. On top of that you can keep your old wheelset and put a different type of tires. This way you have one set ready for fast, flowing singletrack and one set ready for rocky, rooty trails. Or whatever combinations work best for your area.
The drivetrain I wouldn't upgrade until you start breaking stuff. Generally when you upgrade a rear derailleur or something without needing to that is when you will break a derailleur. Generally a couple days after buying the new one.
Other than that just upgrade what you want to, preferably with a goal in mind. Do you want lighter? Do you want more durable? Do you want to empty your wallet?
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