Is there a kind of agreed ranking of hardmode flashpoints from "easier" to "harder"?

For example, I am fairly comfortable with doing the HM Black Talon now, did it several times, last two without wiping. I am a Jugg/tank if that makes any difference...

What would you guys recommend that I try next?

Fallen Emperor is pretty easy, though long and one boss fight has a tendency to get buggy. BP and Foundry are both pretty easy. Kaon isn't bad, mostly trash killing order and what to CC. The bosses are pretty easy.

The two that are harder are Battle of Ilum and D7. Ilum because of the second boss, the rest is pretty easy, though the final boss has a bit tighter enrage timer than most. D7 because the first boss tends to bug, the second has one of those tighter enrage timers, and the last is lots of running around, crazy fun time.

Join a PUG for false emperor. Learn the FP, and then bring your friends and teach them.

Its pretty easy considering you can get the columi chest from Malgus, and a random T1 weapon from HK-47.

I would recommend this order for hard modes, from easiest to hardest:

Black Talon

Boarding Party

Foundry**

Kaon*

Battle for Illum*

Fallen Emperor**

Directive 7**

*Some bosses are harder then the others in the instance, but can be skipped

Battle for Illum - The boss that starts with two snipers next to him is very tough, but you can by-pass him by hugging the walls.

Kaon - The trash is the hardest part, with the exception of the optional boss, which is one of the hardest HM flashpoint encounters in the game. For trash, CC is your friend.

** Buggy Flashpoints (if you run into these bugs, you can Google for workarounds that may work, or skip the instance)

Foundry - this instance can get buggy on the HK fight. Sometimes it won't register your group hitting all 4 buttons, but has worked fine for me on my last two runs.

Fallen Emperor - In the Jindo Krey fight, the BH ship won't always move out when it should. Resetting the instance will usually fix it.

Directive 7 - some classes (snipers, mercs, troopers and gunslingers) in your group cause the first boss to bug out and spawn multipule copies.

Soon as any of my guildies are up for it, I will do boaring party. No one wanted to do it last night, so... we did Battle of Ilum!!!

I would say it was fairly easy. I felt that my gear was adequate, and we only wiped twice once to Krel Thak's shield and once when we hit the enrage timer on Serevin. Considering that for two of us it was the first time running it, it was not bad, I think.

Oh yeah, and Jaesa is going to make me nice Rakata bracers out of the biometric alloy I picked up

You should be just fine if you ran Ilum without any serious problems. The above posters have outlined some common "difficulty ranks" of the HMs.

I'd say that FE is pretty easy, though some tend to rank it as a harder FP. One or two of the trash pulls can be obnoxious if not cc'd / taunted right (Turrets/droids next to Arkis Wode... I'm looking at you), and Nerf turds can hit the fan (HK poison and Malgus insta-kill), but those challenges are about coordination, not gear. As stated, you get tons of loot from FE, so I'm a huge fan. Can be done quickly if you sap some trash and parkour.

Good luck out there!