Said it a few times and will say it again, with engineering and coming to raids with a plethora of consumables, Ret does fine. It isn’t outstanding in any capacity. If you take a full raid of 100% tried and true knowledgeable min/maxers, Ret will sit below most of the DPS. But they offer unique utility and as stated above, can be relied on to show up.
Part of being a hybrid is being versatile. When you’re trying to progress in a raid, sometimes you need to bite the bullet and heal. Sometimes you need a little more DPS. Sometimes having a clutch Lay on Hands or a BoP or an extra body to dispel can be helpful. Ret fills all of these roles. If you are a raiding Ret Paladin, you are prepared for everything.
Now, the fun part. Not every guild is cutting edge or conquering content at a server-first pace. In an ideal setting, you have every Fury Warrior and every Rogue in nearly identical gear, completely BiS-geared, fully world-buffed, with hundreds of gold in consumables ready. This is almost never the case.
Being a guy who takes himself seriously, but not so seriously, a Ret can show up and take 2-handers that might go to waste. They can help heal when a Paladin has to stay late for work or has to take care of his kids. It is a luxury to be a Ret, so should you get the opportunity, you should try hard. Don’t be a Ret that shows up in PvP and Valor gear and expect the first Bonereavers. Be the Ret that rallies the raid. Be a benchmark for the lowest DPS. If there are Rogues and Hunters and Mages below you in DPS, those guys are probably playing wrong. Ret provides a floor for your raid DPS. Sometimes, in rare occasions, Ret might get an insane string of procs and actually top the DPS during trash. Being in the middle to the top of a total raid damage done does help with times. Not every player in a casual guild tries hard. This is where a good Ret will be ahead. A great Ret might actually top the meter on a fight like Nefarian where other classes are constantly disadvantaged by class calls. Not to mention the fun on Nefarian when the dragonkin adds respawn as undead. Launching a salvo of holy wrath and consecrate with a goblin sapper generally spiked my DPS to the ~500 range, pulling ahead of AQ40-geared Rogues and Warriors. People laughed. This was a win/win. Not only did I totally contribute to a kill, I eased the dramas and gave people something to smile about.
When you reach Naxxramas and still get to continue as Ret, you are relatively “decent”. You might put the raid at a disadvantage on a fight like Patchwerk, so you just take a seat and let a Rogue fill in. Yeah, it sucks. You are playing Ret though. You shouldn’t take it as an insult to your manhood. Just be above it. Then when you get to Noth, you’re actually wanted. Because you burst undead adds very fast. Or Gothik. It’s nice to get the nod and watch a Hunter take a seat because you’ll be more beneficial.
And perhaps the best part of being a Ret? Sulfuras.
Every guild needs a banner carrier. Sometimes Warriors will get the call for it. But if you’re a good dude who helps farm consumables, PvPs a lot, brings repair bots, and generally plays hard to win, your odds of getting Sulfuras are pretty good. I’ve gotten it twice as such, so this is just my personal opinion and personal experience.
If you suck it up, don’t complain, and play to win, you’re an asset to any raid, even as Ret.
But that’s not exactly what you’re asking is it?
Viable yes. Meta or necessary? Not at all.
If you’re going to be in a guild with 20 guys who are ranking to 14, and whose goal it is to speed clear MC in 20 minutes, you are going to have a hard time being Ret. You’ll watch their Holy Paladins rank to 12+ with them and wield that beautiful claymore and they will be drenched with tier.
But if you’re in a guild of good souls, who just need someone to make them laugh, and who keeps the drama in check by memeing, and surprisingly does well on certain fights? Well, you’ll get your full T2.5, maybe a Dark Edge of Insanity, and you’ll be a legend.
Take it all with a grain of salt, and don’t let anyone tell you what you can’t do.