So back in the day my devastator marine was grappled by an ork horde.

Now the tables have turned and I am the BC GM and grappled my former GM with a horde of believers.

RAW grappling is a combat action so he could break free, but then only make a half move where the horde would just grapple him again leaving him completely helpless. I agreed that that was idiotic and look into this.

Any suggestions to handle hordes grappling marines?

If you're being grappled by a horde ... getting away shouldn't be easy.

Instead, the sorry bastard getting mobbed should use the grapple check option to do damage, or, y'know, try to move away from the horde. Ask for help from allies, too - while the horde is busy grappling you, it's going to be doing less to mess up them.

Also, I'd probably houserule that yanking the pin on a grenade and then just dropping it at your feet would be doable. Painful for you, but doable. I suggest a frag grenade and being tanky if you go this route.

I understand part of the frustration is the mighty space marine is being hindered by a bunch or normal humans.

One thing i didn't consider is the low WS of the mob means even with out a parry they're unlikely to be able to perma grapple you.

Remember their Magnitude bonus.

I feel stupid for not remembering the expanded horde rules in ToB