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I know this is an old thread, but I thought I would post my experience so far up to lvl 76.
I got a bit lengthy going into details, I summarized everything at the end.
First off, 65+ a Dex Blade is tough and slow to lvl. You fight 1v1 and will often see a knight or other aoe your lvl or just a couple lvls above you mobbing the stuff you are killing one at a time. Also, don't count on getting assists to partner with you since most will only partner with aoe's.
One benefit tho is that you can grab any class within 19 lvls below you and they will get pretty good xp (usually much better than what they can get on thier own - aoes excluded) and you will get the group xp bonus. So when an aoe shouts for an hour for a FS assist or RM, all you need to do is goto the area where charaters within 19 lvls below you and shout, who wants free xp from a lvl xx blade. Some characters may even ask you to give them a message if you need a partner later on.
Up to lvl 60 I had 30-35 str/sta and the rest dex, which worked fine with green weapons and armor. I fought 6-8 lvl above me and exp was quick enough even without a group (though it would have been much faster if I would have know the benefits of contribution). In hindsight, I would reccommend 40-45 sta by the time you hit 60 because starting with fish the enemies hit harder and have alot more HP.
My favorite skill was, and still is Sneaker. I got it around lvl 35-ish by spamming (and thanks to that nice group that wanted the 8th slot filled even tho I told them I was skill spamming). Sneaker isnt all that great at low levels due to the short duration, but its easy enough to get it to a respectable level since it doesn't cause aggro.
The benefit of sneaker is that it slows enemies down enough to use regular NPC bought food between each hit. With sneaker, the only thing that limits the level of enemies you can kill is being able to survive critical hits. I have it up to lvl 18 with very little spamming because I use it that much.
Starting with the fish you will want to start adding elements to you suit(s). Remember to use spros for anything about +3...it sucks loosing armor and you can usually add the cost of spros to the resale of your suit, so long as you add the right element. Electric goes a long way because there are alot of water-based enemies in the 65-75 range.
Adding just +3 electric to your lvl 62 suit will reduce damage from fish by as much as 100-200dmg a hit. If you have non-green sword(s) adding elements to them helps too. I wouldn't recommend adding elements to any green weapons or armor simply because the green stuff usually lasts 15+ levels and any elements could actually hurt your dmg/def if you move onto a different element enemy. Besides, non-element greens tend to sell faster.
After you have around 100 dex start adding points to sta and str. There is not much benefit to adding more than 100 dex. With 100 dex, mastered berserk and a decent assist, you can easily max out attack speed.
Summary
65+ a Dex Blade is tough and slow to lvl.
Have at least 40sta by lvl 60. After you hit 100 dex start adding to sta and str.
Sneaker: learn it, use it, love it.
Starting at 62, upgrade your non-green suits with elements based on the enemies you are fighting.
Hope this helps.