You had some odd/unnecessary movement during early laning that caused missed LHs, like walking way far back and forth for no reason.
Use the hatchet active to pick up distant last hits you would miss.
The farm you get from a 2v1 lane should enable you to get fast Alc Bones, you could've had them at 8 minutes, would've helped your gpm and stole creeps from tree as well. Fast ghost marchers didn't help you that much, as you guys were not actively engaging the Legio. Between pred and slither you should have pushed him out of lane with constant harass with leaps and poison. Also, ghost marchers on pred isn't all that great, the extra stats/AS from steamboots is much better for his passive. And playing against Legio/Ra/Tree your passive will be very important.
~9 minutes you walked to mid, denied a catapult, and walked back to top. A lot of wasted time. When playing a hard carry like pred, don't ever deny when you could last hit instead.
TP around 10:30 was too defensive, slither was there and together you guys probably could've turned that.
You hardly used your ghost marchers, if you buy them, spam that speed when you know you won't immediately need it for fighting heroes, like when you're walking to the lane. Time is money, and faster ms means more time to farm. Ghost marcher speed has a 50% uptime if you spam it. After you leap, make sure you hit it to get those extra attacks in.
It's good to want to kill the carry, but every time you chased FA around and failed to kill her your team died in the process. Pred's passive lets him DPS down the tanks while healing for tons of health, maybe you should've taken the kills and assists you could get with your team and leave the FA for later/last.
Helm on Pred isn't too good, also. Yeah, it's a great item against FA, but if you picked up insanitaurius (sp?) instead you could've had Armor, Health, and AS for your passive to make up for the damage you take. I also don't think this was too much of a shrunken head game. Pred's skill is enough to counter tree, and the only disable after that that was really screwing with you was Frostwolf, which shrunken doesn't save you from. MKB/Insan/Steam would've given you just as much HP and way more damage. Frostburn was a good pick up though, although shieldbreaker might have been useful to go through the Helms on Legio and Ra. You were in a really hard spot after FA finished Frostwolf. Geo/Frostwolf on any ranged carry is pretty GG for any melee carry that isn't magebane.
More focused on GPM, I noticed you never killed the ancients, when you notice the opportunity, head over at X:50, stack and kill them. Pred can do them easily.
Wasn't much you could've done though, you guys were 4v5 with the worthless arachna, and FA was a smurf. NT.
PS: With regard to GAFIH and regulars not going easy, this has been said before, and I'll just reiterate it: We are NOT trying to smash people, we pick heroes to mess around on/get better at and just play the game in a relaxed fashion. It's hard for those in game to give direction to those learning, that falls mostly to the specs for in-game stuff. Generally the best advice is to stick with your team. At the time, those of you who are new can't expect to be told some enlightening set of instructions and get much better at the game. It helps, but only experience really makes you better at this game.
PPS: Not dead.