Well, I think it's time for some feedback. I'll try to be as civil and constructive as I can
"The Flea" AKA 3PV challenge: I think enough has been said about it already. I'll just add that there is a line between being original and being crazy, and PGI stepped way over that line with this challenge.
"He's dead": Earned naturally through normal gameplay. Nothing special, and no real effort involved.
"That's cool, right?": That's a challenge, right? Just equip Coolshot 6 in one of your consumable slots, and gulp it at the beginning of the match. Repeat 11 times, and your're done.
"No, not cool.": Quite easy to achieve, too. I did it with my dual peeps Shadowcat which is naturally prone to overheating, but has good survivability due to being an ECM medium. Just overheat once, hit override, disable override once your mech restarts, and keep playing normally.
"She's just drained.": Very easy to cheese. I just dropped a heatsink from my 3xcLPL Hellbringer, put one cSRM2 + 0.5 tons of ammo in its place, made sure I depleted it at the beginning of the match by shooting at the ground, and continued playing normally after that.
"Dustin Farted.": Seems like a regular cumulative challenge, but something's weird about the way it registers in-game time. It definitely took me much more than 10 hours of playing to get this achievement, was probably closer to 20.
"I'm the Monster", "Monster Hunting", "Like a Ninja" - I skipped those since I don't normally use narcs, tags or play lurm boats.
"Sensory Deprivation": Can be done with UAVs, if you don't have an ECM mech or don't feel like playing one. A bit tedious, but there are usually enough enemy ECM mechs running around to counter.
"Hawkins Energy": Very easy to achieve if you are also carrying advanced seismic. Once you see a red dot on your seismic, just deploy a UAV and your're done. For those who regularly use UAVs in the course of normal gameplay, this isn't even a challenge.
"Keeping the Curiosity door closed": This one's a bit tricky, because you have to rely on the enemy to deploy a UAV first, and then you have to kill it before your teammates do. Too situational for my liking.
"We're just friends": Another easy challenge. Just pick a buddy from your lance, stick with them, and make sure you engage the enemy at the same time they do. Can feel a bit restrictive for those players who like operating on their own (like ECM snipers), but there's nothing wrong with encouraging closer teamwork.
"Friends don't lie", "You're my best friend, too": Earned naturally when playing mediums and lights. Nothing too special here.
"Castle Byers": Not really challenging per se, but very frustrating, and a huge pain in the behind. With people generally hating conquest and voting against it, and with assault games rarely being won by capping, you have to get literally everything working in your favor... and then repeat it 11 times. Way too situational, and almost totally out of the player's hands.
"She flipped the van": Not too difficult, since you only have to do it 3 times. Still, requires some minimal skill and commitment.
"You promised", "R U N": I never paid much attention to these ones, until I realized that I've completed them. I guess it's another pair of objectives that are achieved naturally in the course of gameplay.
"The bad man's gone.": Reasonable. KMDDs have been a part of most challenges for a while now, and for good reason, as they represent the player's skill better than simple kills.
"I found the chocolate pudding!": Very challenging. I think this should be a top-tier challenge with a really good prize, like a mech or at least a mechbay. Would have been much easier to do in FP, because you have 4 waves of mechs... If only FP wasn't so broken at this time. Our unit could barely get a few drops in over the weekend, because we constantly kept running into that dreaded "Can't find match" bug (or whatever the exact wording is). I hope PGI fixes it before the next FP event.
"Keep it locked down.": No idea how to get this one, and I won't even bother trying. I think it has been commented on in this thread already.