So as an update...
My current buildup at Lv. 39:
I know usually one would just go DPS and then learn to tank at lv55, but since I don't play but maybe once or twice a week, I've found that a half and half build is advantageous for those desiring to do FPs and Heroics on the way up. It isn't as gimped as some things. Sure as builds go it foregoes a lot of perk advantage, but it isn't unworkable. And it has been at least somewhat successful for me. However I've found you need to have great to EXCELLENT healers. A much-more-than-competent healer is ***critical*** to tanking as a shadow. Period.
I've found that Lv. 30+, one can actually keep up at a decent pace if they're smart about it. Shadow Tanking requires a bit of thought and tactic at all times. By its nature you have to constantly be on the ball and cannot lose the edge. In fact...it really seems to get your mind in shape. (Practice!)
Wasn't sure I liked that sort of challenge but can definitely say it isn't as boring as slogging and grinding away by just jumping in. Still comparatively frail but when survivability is more about wits and staying alert, it actually is more fun that way. Certainly makes a difference in PvP for what few times I did it.
Caveat: A pain to deal with are enemies mid range tech damage types using flamethrowers when you only have a comp like Cedrax, or a trooper player who is not primarily a healer. Such as Bounty #1 on Coruscant. Since my melee damage is slightly more than my powers and being limited at mid to close range, sometimes it even gets frustrating.
Since the high-maintenance management style of shadow tanking also requires easing up/dissecting enemies in groups I've been able to actually juggle numerous enemies at once on my own that might otherwise overwhelm other characters like my gunslinger Charlievarick (a nod to Charlie Varrick, Walter Matthau's character in a '73 movie). I can now confidently move in against two at-level golds, or multiple silvers. If I outlevel a champion, sometimes I can take that group down alone with a comp if I outlevel it enough. Barely but still able.
I digress. Dissecting groups of enemies also requires very good communication with your DPS. Some of it is common sense and should be a primer prior to doing any MMO but some people still need to be taught apparently. Everything has to be surgical--that's the only way it works with shadows.
So how is Shadow tanking going for you now, especially since Shadows lost their self heals with 2.4? IMHO Shadow/Assassin tank requires the most ability management out of all the tank classes in SWTOR.
Challenging for sure but I haven't known how it is to self-heal. No wonder Shadows and Assassins were considered OP initially.
Very tight rotation for sure.
I have done...I think it was a detention level in Nar Shaddaa without a healer and one of my DPS even DC'd. But we managed to get through it. Slow as all hell, but we did it.
Yeah, one has to be very selective about which abilities to improve when leveling up. Probably won't do for upper level ops and the like, but as a toon leveling up it works great. Since Shadows are meant to be up-close I tend to put more into closest range abilities, but the disabling abilities have to compete for priority with abilities which give you back HP and FP on attacks. Also being half DPS I have to manage to work that in as well. But it's a versatile recipie, and it's nice to actually second or sub tank alongside another and switch to damage as needed. A couple times when the main tank has fallen, I took up the slack. Or if the main tank isn't doing his job and the healer gets nailed, I can battle rez. Even if the enemies regain all their health, there's something to be said for not having to medcenter it every time when you wipe.
This is probably redundant but I wouldn't say this if I didn't think it was important:
Some things I've learned as a novice tank. I've also watched my roommate do the HM dread master ops, 16 player co-op. These are consistent observations.
1) Don't jump in and aggro the whole area. Especially if you're not the tank. Tanks have limits to how much damage they can absorb, and a healer(s) cannot keep the tank (and invariably the rest of the group) alive if they're receiving damage faster than the healer(s) can counter it. This is especially important if the tank is a Shadow. I don't appreciate it when I'm staving off 5-8 enemies and someone goes and pulls another 3-5 enemies. Nothing pisses off a healer more either, apparently.
2) PLEASE DON'T attack the champion I just stunned in stealth, especially if there's multiple golds in the area. I cannot tell you how many times this annoyance happens. I'm not a power tripper, but if I say don't do it, DON'T #%$@ING DO IT. Also, let me get their attention first before you jump in. Sentinels, DPS Guardians, DPS Troopers I'm talking to *you*.
3) Keep away from the front of of enemies. If the enemy is a boss with a 'rage' timer, I need you to cut him down fast before time runs out and it's a wipe. You can't do that if you're dead!
4) Instakill one-shot attacks, and percentage damage will kill you fast regardless of your durability. Get out of the way. Yeah I can Battle-Rez as a shadow, but if the enemy's attention goes off me as a tank, then everyone else dies.