There's a huge difference between flesh wound and coughing up blood. Even Netero was able to cause flesh wound to Meryem, and Netero's physical attack power is nothing special at the Royal Guard level. Meryem can take Netero's hit while sitting still but he's still *wounded* the same way Kite *wounded* Pitou. We don't even know if the blood was Kite's or Pitou's, not that it'd matter since such trivial wounds have no effect on the physique of a Royal Guard.
If anything Pitou is easily the strongest of the Royal Guards, though his abilities might be ill-suited for fighting as his ability seems to be geared to solely help the King. Consider:
1. Pitou is said to be stronger than Netero by Netero himself.
2. He maintains an En of 1km+ radius day and night, and clearly has the largest En out of all Royal Guards. While En radius does not imply power, there's no way you should assume a guy with a smaller radius ought to be stronger. After all, En is basically just an extension of your available aura.
3. When being punished by Meryem, he appears to shrug off the hit most casually. In fact, Yupi's the only one who complained about getting hit sucks out of the 3 RGs.
4. He uses Manipulation techniques to control Meryem's army, despite the fact that Pufu is a Manipulation user and ought to be better at doing this stuff. Pitou's Manipulation ability is also more advanced than Pufu, as he can manipulate memory while Pufu cannot (this is why Pufu doesn't actually mind Palm betraying them because that'd mean he'd no longer need Pitou).
In the actual fight it is said that Yupi is more than 10 times more powerful than any of his opponents, but he still cannot connect a hit. Pitou, however, is said to be able to kill Gon in one hit anytime he wanted to, and the only reason he didn't do that was because Komugi was taken as a hostage. Pufu, on the other hand, would actually lose to Killua at 1/14 of his full power (clone contains 1/7 of his self plus 50% penalty for not directly controlled). We can also infer that 50% of Pufu's power can be defeated by 'several guys as strong as Morel', according to Pufu himself. Given Killua beat his clone, it'd appear he's most certainly not 10 times stronger than his opponents.
Pitou's ability might be least suited for combat but in terms of raw power, he is easily the top of the Royal Guards. Based on the damage all 3 RG took from being punished by Meryem, there's no apparent difference in their ability to withstand damage.
Now moving on to Gon. It doesn't matter how Gon did that kick. The point is he is able to focus enough energy in a single kick that surpasses what any human level character has been able to do (the only being that could possibly wound Pitou that seriously in one hit would be Meryem). Yet immediately after doing that he still went through the same motion to prepare for Rock. This means the charge time restriction on Rock is absolute. It cannot be related to experience because we see he can put enough aura in a single kick that surpasses any human level character can do basically instantly, so in that transformed state Gon has the ability to concentrate an amount of aura that far exceeds any human can gather. Yet even with this kind of incredible power, he still needs time to do Rock.
---------- Post added at 04:57 PM ---------- Previous post was at 04:46 PM ----------
Well, the issue with the charging time being a restriction is that it has never really been said. It was suggested by knuckle but we do have to consider that it was something he said based on the information he had. The only character that can really confirm time to be a self imposed restriction would be gon so far. Gon has never made the point that the charging time is fixed so far. More so in the very knuckle fight we saw that the charging time was not a restriction in the end, it was a flaw that needed fixing. Even killua agreed that the technique is ordinarily useless. Heck, the only reason gon was able to use it was that he used cheap tricks which won't necessarily always work.
The position gon takes, his battle cries... those could be considered restrictions as it would make perfect sense they have an effect on gon since he does those because he genuinely likes it. In turn the time it takes him to gather nen for his ko could easily be attributed to his overall lack of experience using nen altogether. I don't think the manga has been anywhere near conclusive enough to suggest the time to charge ko is a restriction considering gon's hatsu as a whole is still in its developmental stages.
If the time to prepare for Rock is due to lack of experience then when Gon is transformed, he should've just hit Pitou with Rock on the first hit instead of kick him into mid air and then do Rock. After all Rock is still his most powerful move. Trasnformed Gon has a mastery of aura that easily surpasses any human character in HXH, as he can focus enough AP to do serious damage to Pitou nearly instantly. Yet even with this level of expertise, it was not possible for him to simply do a Rock under the same opportunity (otherwise he'd have done it instead of kicking Pitou first). The frames in the Rock sequence show that even transformed, it is not an instantaneous process to focus this much energy.
Now of course if Transformed Gon just wants to do 2000 AP worth of damage, which is what his Rock does as a child, he can certainly do that at will. But if he wants to do more damage, he is still limited by the Rock's charge time. Keep in mind that Gon is probably aware his transformation can't possibly last very long, so although he certainly has a huge upper hand just using normal moves against Pitou, he absolutely has to end that fight quickly before the transformation effect runs out.
He just transformed, became some sort of monster with tremendous aura, but his battle experience was still the same. He most probably had a hard time controlling himself during that time because of his inexperience.