"You're a standard all the way"

I've never done it but I always here it's one of the best investments for your game. Also it sounds like this guy doesn't know his stuff or was lazy and didn't want to fit you. The main determinant for the length of your clubs is the distance from your wrists to the ground when hanging at address position. So a 6' 5" guy could have clubs shorter than standard if he has some monkey arms!
 

You should at least get fitted for the correct length and lie of the irons, ping has a great system with multitude of options. 

I'm 6'5" and my clubs are 1/2" long (but 5 degrees upright).

I guess I don't quite have monkey arms.

    There is no way of knowing by height alone. Tom Wishon, one of the top club builders advises against static fitting (measuring someone's height, setup without swinging the club) because body position can change during the swing and thus the numbers you get at setup may not have any relation to your impact position when you are actually hitting the golf ball. Personally I have never had custom fit clubs so I cannot speak to whether it may help or hinder but I am 6 4" and I play standard clubs without any issues. 

IMO directional problems are not a result of the grip but rather your alignment, set up, swing, etc. Post a video or two of your swing, there are a lot of guys on TST that can provide really good insight into what your problem may be. BTW, I don't think you are a "standard" judging by your description but I think you really need a dynamic fitting to tell.

Get fitted.  You won't regret it.  It will also give you some knowledge on the state of your swing and what you need to work on.  Find a good fitter though.

 

A good example is a bicycle.  Most people would just buy a bike that is close to the right size and go from there.  But, if you want to be comfortable riding really fast, for a long time and not injure your body, you need to fit the bike to your body.  Bikes are adjustable for this reason.

 

Same applies to golf clubs.  If you just want to hit balls every once in a while, then off the shelf is fine.  But if you really want to improve to your potential, then a fitting session will make adjustments to help you down that path.  You may end up being close to standard for length and lie, but a fitting session will tell you this.

Golf club sales dood probably tells everyone that because he wants to get back to his smoke break.

I also believe getting fitted is a must when buying new clubs. I had two fittings one week apart. The first fitting my swing was awful, my stats were the same from my fitting last year + 1/2 length, up 1 lie, and stiff steel shaft. I decided to go to a different golf shop
Friday. My swing tempo was smoother and I
was hitting the irons square on the face. My length was standard, but my lie changed to standard and my graphite shaft changed to stiff/regular (Mizuno JPX 825 Pro irons). My
second fitter was telling me a person's stats can change if you are swinging better and for me, swinging graphite shafts.