[R_Squared]

Its a mini green tide in effect. I doubt whether it would attract the same amount of firepower as that formation, but I also doubt it could tank the same amount of hits as the GT. It's getting close on points too.
An unenhanced GT is 660 points.
With a Painboy, Warboss with PK & Big Bosspole, and 1 PK Nob you're looking at 796 points.
That's 250 points over that unit, but with 70 more boys. Even without Rampage and EA, that's a lot of extra boyz for your points.

However, when you start adding in Shootas and Rokkits it starts to really pile on the points (859 for 3 units kitted out)
Chuck in some EA and you're talking a whole army in one blob.

Interestingly, your Blob, plus another blob consisting of a warlord BBP, PK and Painboy would mean 2 large, heavy immovable units of Boyz, for about 1000 points (ish) which backed up with some fun combinations from the Heavy lists could give many armies a real headache.
Not very flexible or quick though.

 

[R_Squared]

That's why I resist the urge to stack eavy armour on my GT, great against bolter fire, but not much else. FnP is a much more cost effective and useful alternative. If pain boys weren't HQ choices, and we're non-force org like meks, I'd put one in every unit.