There's a larger discussion to be had here, I think, surrounding player expectations of success / failure. At what level is it "acceptable" for a character to fail at a given task?
I don't think that is the heart of the matter. D&D _usually_ is binary pass/fail in terms of proposition resolution. It either works or it doesn't and it doesn't pay much attention to the niceties and complexities of degree of success very much. In some cases, this has really bugged people. For example, how much damage you do doesn't really relate to how well you hit something. D&D doesn't consider hitting something and doing damage to be really separate simulations at all. The first 'to hit' roll is binary, and then it discovers how well you hit.
But for now, let's imagine a generic system that tried to resolve degree of success in all cases. In such a system, the '65% success rate' you mention doesn't necessarily mean much, because often we care about the degree of success before we know whether you succeeded in a meaningful way. You might succeed in hitting the target, but the degree of success wasn't enough to overcome the targets armor.
Usually such systems have a range of results for any action you take.
1) Critical Failure - You tried to do something and made the situation spectacularly worse - shot yourself in your own leg, for example
2) Failure - You plain failed to accomplish what you were trying to do. You shot and missed.
3) Failure with mitigating factors - You failed to accomplish what you wanted, but it wasn't all bad. Your target lost his balance when dodging your arrow and now he'll be easier to hit on the next shot or otherwise hampered.
4) Success with complications - You succeeded, but not in the way you intended or not without problems. - You shot your target but also hit your friend, or lost your balance and now are hampered, or you hit your target but he yelled out and summoned reinforcements, or whatever.
5) Minimal Success - You grazed your target doing real but minimal damage.
6) Greater and greater degrees of success - Usually such systems have several different ranks of success. For example damage might be computed by multiplying base damage by the degree of success (x1, x2, x3, x4, etc.)
7) Critical Success - You got lucky and hit the 'I win' button. Your target is dead or dying.
Now obviously, game play will vary greatly depending on the particular percentage chance of not only that you succeed (whatever that means) but of each particular category. Often games of this sort in my experience end up revolving around 'Who gets lucky and rolls critical success first?' because they make the odds of critical success too high, especially at higher levels (where it also often turns out that foes have such spectacular defenses that really only critical successes can work anyway).
Consider games with 'Fail Forward' highly privileged as being particular cases of the above. Typically they have the appearance of binary pass/fail mechanically, but they have a strong exhortation or guideline to privilege #3 and #4 as results in the 'fail' case. As a result, they tend to play out something like this:
1) Critical Failure - 0%
2) Failure - 0%
3) Failure with mitigating factors - 25%
4) Success with complications - 10%
5) Minimal Success - 0%.
6) Success - 65%
7) Critical Success - 0%
Of course, a lot of this isn't actually hard wired necessarily but left up to GM interpretation so depending on the GM you could all sorts of actual results in play. Note that typically #3 and #4 in other systems are rare results just because they burden the GM somewhat harshly in my opinion.
I should also note that I'm somewhat simplifying this. Umbran is correct in that generally 'fail forward' is not applied on the level of individual rolls of the dice, but on the level of scenes (a combat, a negotiation, etc.). You generally wouldn't see fail forward applied to every sword swing in a combat, although the thought of what doing so would be like does somewhat illustrate some of the reasons I'm not a fan of the concept applied generally even at the level of scenes.
Basically, the point of the technique is to caution the DM against thinking that 'nothing happens' is the correct way to narrate failure and to keep the game from getting stuck in an uninteresting place. There is a lot of high minded philosophizing around the idea that failure shouldn't suck but should be fun that I think is a bit too utopian though.