Till this day I see people using PGrens wrong, this is probably the biggest problem, not their actual strength. There are quite some good players who gave them a shot and use them in a good way, Twister is one example.
PGrens should not be able to frontally charge another squad and kill it, as this causes PGren blobs and does not fit to the tactical elements of unit positioning. That's why they were changed in the first place - They were too strong and in a way that broke the game. To compensate, they got a higher damage, but less durability, meaning they need to be handle more carefully now, but can be just as devastating.
If you take a look at the graphs (
http://www.coh2.org/topic/6598/coh-2-dps-spreadsheet/post/175221) or the values (
https://docs.google.com/spreadsheet/ccc?key=0ApmrrrPr20ncdGF4VURuYjVGZXlIN3ptbV8tbzRzN0E&usp=drive_web#gid=0) you can see that they start to have more damage than Grens already at 31 range. At this range they already perform better than baseline Grens, but they do not perform better considering their cost. If you want to add that in (340/240 => ~1.5 times better) you get roughly such a performance already at 22 range. Since they also take less damage (and it's not 1.5, but a bit less) at such a range they already vastly outperform normal Grens.
Now you have to take a look at other factors as well, like the LMG42 upgrade for Grenadiers and let's compare the DPS. Once again, we artificially increase the DPS of Grens by a factor of 1.5 to take the higher cost of PGrens into account. We'll see that at the range of 15 the PGrens once again start to be better. That means even compared to an upgraded LMG42 Grenadier, PGrens outperform it per cost at <15 range in regards to damage dealt.
Why is that so important? Because a lot of people tend to get really close with their PGrens, lose one or two entities to do so and then of course deal minimal damage, have to retreat and complain about the unit. That's false use. Go to ~15 range (That's roughly half the vision range as a rule of thumb) or to a similar distance if there is better cover. Don't close in further, as at that range you are already in a good spot and closing in further greatly increases the damage you take in the process and the chance to lose an entity. Staying at such a range usually yields the best results.
Yet this is just one of the roles of the PGrens and actually one where they perform worst. Besides that they are a great flanking squad. If you manage to actually get close to the enemy without them firing on you, do it. The closer you can get, the better usually(exception vs SMG troops), yet only if you can do so without being fired on. Closing in under fire => losing entities => higher MP drain for you and actually often less DPS than at a longer range.