In Haqq, i usually put one of them on the table, either doc with the bot or a doc in the fireteam, the latter mostly being there for pushing buttons. Also in RTF Hakim is the cheapest midfield specialist. In Ariadna or Dashat i dont bother.
A doctor / Engineer + a single strong ARO or long range attack piece = value. It helps reduce the potency of crits. If your hexa sniper pops out of hidden deployment to blast some fool, and gets critted on a 1... Trauma doc is there for you, friend.
Last tournament I played in I misjudged a first turn Impetuous move and my Spetsnaz got taken Unconscious by the splash from an HRL, I was very glad to have a 112 standing ~4" away, and even more glad when he passed his WIP roll.
I generally have a personal belief when it comes to doctors and/or engineers: If the model isn't going to leave my deployment zone, I will have something that can bring it up nearby; If the model is going to stay on my half of the table, I will try to bring it up if I can; If the model is going to push past the half of the table, I will consider it's death a certainty and not bother with bringing it up. There are exceptions, though: Avicenna and the Reverend Healer are usually right next to the big gun they are pushing past the center of the table with, so they can bring those big guns up even after they crossed the "no go" threshold. Same thing for say, an Anaconda twoing an engineer together with it. So yeah, like everything else in this game, the answer is usually: "Well, it depends..."
The point of view are very different in this game. In IA I almost always take a doctor (and an engineer). Normaly with a helper bot. They help me to patch up my downed troopers. In case of the fake HIs like the Haidao, it´s a bit risky, but normaly works. But I prefer a doc in most of my armys. In ISS the Sopho is important, because she is also a quick and durable specialist with high WIP. My Nomads - normaly Corregidor - the Daktari has to bring the Intruder back on his feet and the Tomcat Doc can patch up troopers in the midfield. In most cases Daktari is enough. My PanOs have some troops, that are worth doctoring too! So yes to the doctor!
To add a little more, I think the main factor you are looking for when considering good troopers or a good list is value. Doctors and engineers cost little, but may provide , essentially, an additional wound (or multiple) to an already valuable unit. They are force multipliers. If your sniper goes unconscious, and you revive him in 1 order, you have paid for the order you just spent by getting that snipers order back in the following turn, re add an important tactical piece for your active turn, and likely cost your opponent 1-2 orders if they have to remove the sniper again. This will work in your favor more times than not over the course of regular play. Cubes also help mitigate your losses on the dice rolls.
That's it. It does cost you one order (or more), but the important point is either how many orders do you save (ie: not having to move someone else to do the job the doctored troop was doing) or how many orders will it costs for your opponent. This is the same as engineering a TR remote back into life. I like it when i put some HI for ARO duty behind a low wall, because they are usually expensive, strong, have powerful weapons, and most of it: have shock immunity (by being HI) and can fall unconscious out of sight so that the opponent can't finish them. Powerful HI used for ARO duty are made better by having a doctor/servant close to them. Mk.4 HRL, HRL Al'Fasid, Feuerbach Azra'Il ... I guess it would be worth even for an army with "bad" doctor like PanO if the mini is really worth spending an order and maybe command tokens, like ML swiss.
I think it's as simple as this: if it's a mission where you need points on the table to win the game, take a doctor. If not, then it depends.
I err on the side of always taking a doctor unless I'm playing a crazy bot list with virtually no biological beings on the table. Docs are just a few points over a normal order-monkey-grunt, and they provide resiliency for key pieces and a possible Classified. When the Daktari became a wildcard in Corregidor, she went to the top of my must-take list. Plus the model annoys people who aren't into anime catgirls and that's always a plus. She goes into Alguacil linkteams most of the time, but sometimes she joins the Senor Massacre Assault Squad to get a cheap specialist and combi in there.
No doubt, that she is of value in a link team but sometimes it is contra productive to aktivate her in a link becaue you have to take precautions that no one is in LoF and gives a free ARO to the opponent. I would run her in a link with 2 or more Brigadas. For Jag and friends I would pay a bit more and take Lupe. But as always it depends on the list you want to build and for what mission. In Supplies she is gold with the Jags.
Revival/restoration crews that you don't intend to double-use as button pusher is probably worth it if he stays away 1 order from specific target without which your gameplan can suffer. Engineer with a helperbot looking after that TAG which just ate 1/3 of your points, medic that walks with your fireteam (although in that case he probably does double as button pusher) - those are pretty safe to field and to use. Excessive doctoring may be a noob trap, however, so watch out*. If you don't need that Unconscious guy doing something now, including scoring with his warm body, then you probably don't have to bother. On the other hand, if your opponent knows that you can get back your link bonuses or specialist options in 1-2 orders, he may decide to spend extra 0,5 orders every now and then just to shoot the bodies. That's actually enough value out of those ~17 points docs usually cost (or 3 points if being a medic is an upgrade over other profile). You don't even have to risk actual doctoring rolls to get that value in that case. * - insert obligatory joke about how Haqq have the best docs and no models worth orders spent to bring them back