Contrary to what is claimed p/p can inflict considerable damage but it is very lacking in the defenses and mobility. You will find a number of weaknesses.
1>lack of mobility. Most sets have an evade or a port . P?P has none of that so you have to rely on utilities for the same and in particular withdraw and RFI.
2>Ini hungry. Unload is your major source of damage and eats the INI. At the same time your main defense from the set outside the range is blind and that is prohibitively expensive. Unlike d/p where you can use blind then an HS for stealth to set up a backstab the blind really does not set up a larger attack on the p/P set.
3>Lack of stealth. This means the enemy will always see you and always lock on you. There are other sets that do not have great stealth but they have ports and evades that can help disorient an enemy integral to the set. You have no such thing in p/p. They see you, they target you.
4>Lack of condition cleanse. You will find this more significant in p/p than in other non stealth sets simply because you have fewer ways of avoiding the conditions being laid on you when they come your way. Shadowstep has a very long cooldown and will not be enough for anything outside PvE.
To mitigate these issues you should consider some combination of the following.
1>access to stealth. The only way you can do this outside using an alternate weapon set or a utility is trappers runes.
2>More Condition cleanse sources. Consider trickster as a trait in trickery. With RFI and withdraw you have two more cleanses. I would also consider some combination of purity/generosity/cleasning as sigils if doing anything outside pVe such as WvW unless you plan on running with a zerg. In Pve you generally do not need a lot of cleanse.
3>Sources of health coming in. You can not rejuv and you have far fewer ways of avoiding damage than other sets. As such IP or Food that gives health on Crit or a sigil of blood or leeching can help here.
As to Crit chance I find the higher the better with a P/P set. I would go for around 60 base as you really want your unloads to hit hard.
The runes of the eagle are very good damage wise but you can also consider Adventurer which can give a few more much needed dodges, trappers for stealth or Wurm which add both Vitality and ferocity.
I personally found Speed to be a great rune . You do not inflict as much damage but the 25 percent extra speed boost is extremely helpful in battle along with that swiftness. There nothing worse then having a person near death and then having him run away and get away because your foot speed so low. You also get the vitality boost and can sub out your valkyrie gear for more zerker or assassins.
Now you mentioned you do both Pve and WvW. Most of my advice is oriented towards WvW. I found in PvE you can get away with a lot less in the way of defenses and condition cleanses. This changes up a bit in the dungeons of course but if you take a build that works very well for you in PvE and try and use it in WvW you will find yourself dying a whole lot more and especially with a set like p/p.
