Ah the raven, another one of those mysterious units that has so long gone completely un-used but for a narrow range of 1 base TvP all-ins but then just out of nowhere or out of necessity has come into standard play.
The reasons for the Raven’s appearance in the current metagame can decisively be traced to terran versus zerg, a matchup that really has been driving terran unit compositions for a long time. You have to go as far back as to the infestor buff where the duration of fungal was cut while the damage remained the same, a seemingly narrow buff that has ended up shaping all of the current meta game. The fungal change immediately resulted in infestor/broodlord absolutely destroying the terran late game of the time. TvZ was pure marine/tank/medivac all the way to the end with the addition of vikings to deal with broodlords. But with a stronger fungal this lategame composition became increasingly powerful. People tried to adapt by splitting their vikings but the fungal change really had nothing to do with vikings, what the fungal change did was to create a buffer zone for the broodlords where marines could not just stim in under the broods and target them down anymore, leaving only the vikings alone to deal with the broods. This in turn meant that zerg could now spend more on corruptors and since vikings were the only thing that could actually kill the broodlords, maintaining air superiority assured victory.
Enter the ghost, so this is where terrans figured out that the ghost is really good. This is how it usually works for all races in sc2, either a buff or a necessity will bring out a unit that has previously not been used much at all and even if a unit like in this case comes into play due to one matchup it usually has fallout on the others and ghost usage increased substantially in TvP as well. First terrans attempted to use ghosts in late game TvZ as a means of emp’ing or sniping the infestors but this method just was not solid and pretty much relied on zerg lacking detection. But then people figured out that snipe was really damn good against broodlords, and ultralisks as well solving both the broodlord problem but also another problem late game TvZ suffered from, the dreaded broodlord into ultralisk techswitch where you were stuck with 30 vikings when the ultras came rolling in.
But then yet another patch changed the scenery once again by effectively making snipe an anti caster ability only where the only cost effective thing to use it on was infestors, which had already previously been tried and failed. At the same time though the raven seeker missile was given a subtle buff by being given increased speed. This change has gone unnoticed for quite a long time and only relatively recently has the raven started to come up more and more as the solution to many TvZ issues.
Basically I would argue that the Raven is the best terran tech unit. All units with energy are extremely valuable in the late game if you can retain them but the raven is both a flying caster and also a very versatile one. People figured out very soon that seeker missile was amazing against broodlord tech but the switch to a raven based late game has still not really come around mainly because it is awkward to make the transition into ravens when you only make them against zerg’s tier 3. Ravens take a lot of time and resources to make and you need 2 upgrades and I think this is why we are only now seeing ravens done the right way, specifically people are trying to incorporate the raven much earlier into the general game plan, way before tier 3.
This brings us to why the Raven is most definitely destined to replace the tank in terran versus zerg. Let’s talk about the problems with the tank for a moment. In fact in any situation where terran is not going mech, tanks are actually pretty damn useless. Terran’s and zerg’s alike started to figure this out when the heavy ling styles started to become popular, the only real reason people make tanks in TvZ is because of banelings. If you don’t make tanks you will die to 70% banelings no matter how well you split, beyond this though the tanks is very bad at killing almost anything else unless you are fighting in an extremely favorable position. Bio which should be the go to unit composition for terran against zerg just as it is versus protoss gets crippled by the necessity for tanks, the amazing mobility of bio can’t be utilized because the army needs to move with the slow tanks which reduces the mobility of the bio to harass drops.
So if the tank really is only there for banelings, and the seeker missile deals just as much splash damage to banelings as it does, why are we not replacing the tanks with ravens? This is what Bomber has started doing, going for an sk terran style from bw consisting of bio and ravens and I think this is going to be the standard very soon. If you just skip the tanks completely you can add in the ravens much more naturally and much more early on. The ravens are fast and allow the bio to be as mobile as it can, meanwhile the raven is good against a lot of other things beyond just banelings. I think that one reason why people are hesitant to use seeker missile against banelings is that you convince yourself that because the missile does not hit instantly like tank splash, people will just run away from them and they are useless. Well, considering the fact that if you unload 4 seeker missiles against a ling/bane clump rolling down on you, it takes a magician to be able to tell which units are being targeted and split them away. The zerg can really only chose between taking the damage or pull everything back, if you wait long enough to fire ze missiles, running away is surely going to be a bad idea, in an ideal engagement you are probably dropping zerg in more than one location at this time, and if zerg turns around all of the stimmed bio is still going to be chasing stuff down.
If the Raven can work as a core unit for the terran army this is in time going to make players really utilize the unit to it’s full potential. Once you have ravens in your army you are going to find more ways to use them since they are already there. Seeker missiles on saturated mineral lines, constant and incredibly annoying auto turret harass all over the place etc.
I am currently trying out the bio+raven style of play myself to get the feel for it but I have a strong suspicion that this might be more and more common on the ladder.
Vanguard 