Which kinda proves Falkas point since if the difference of whole 6 attribute and 2 skill points of Power strike doesn't result in much damage difference, there's even less point in putting it into PS.
Well if you pump 6 attribute points into strength in order to put 2 skill points into PS and not IF, you get 6 hp (at essentially no cost) and a 16% damage increase. There is no way to get a "free" damage increase. Let's put it this way... sure IF can be useful, but if you have 1 skill point to use and you just hit the next multiple of 3 for strength... do you put that skillpoint into PS or IF? Look at it this way, PS gives you an 8% increase in damage output, regardless of the weapon you use. IF gives you 2 hp, regardless of how much hp you have. So at level 1, with 38 hp, that 2 extra hp is only ~5.3%. Now what if you have 18 strength, and put your first point into IF? Then that is only a 3.6% increase. The trend continues onwards, of course, where 2 hp becomes a smaller and smaller increase with respect to your total health. PS will remain a constant 8% each and every time you spend a skill point on it.
I think we have kind of gone off on a tangent here, discussing whether or not you should invest 7 points into +3 agi/str and then +1 WM/ATH/PS or all 7 into IF. I sure hope having 7 points in one skill would prove more useful (which is still debatable, imo) than having just 1 in any other. As others have mentioned, someone who knows how to use speed bonus really well might get way more out of just 1 more point in athletics than they ever could out of 7 in IF. With a ton of athletics you can avoid getting hit at all, or always giving your opponent negative speed bonus so if you DO get hit, it barely even hurts, regardless of the fact that you have little to no IF.
To prove my point (which is merely that IF is the weakest skill) just think to yourself, as a melee build, how would you rank the importance of IF, PS, Ath, WM?
Imo, they would be:
1. Athletics
2. Power Strike
3. Weapon Master
4. Iron Flesh
Athletics and PS are definitely really close, and I would say that at lower levels each increase in PS is more advantageous than athletics, but once you get past 5 PS or so, athletics becomes more powerful. As for weapon master, once you get past a decent amount of wpf... around 140 or so, then you are pretty much set, and anything on top of that is merely bonus. IF however just never seems like an attractive option, or something that you look forwards to after leveling up. When one of my alts gets a new point in athletics, PS, or even WM, I practically jump for joy. Another point in IF makes such a small, unnoticeable difference there is no reason to look forwards to it. That said, sure jumping from 0 IF to 7 IF is awesome... but compare that to the difference from 0 PS or 0 ATH to 7.