I don't get why champions like Alistar, Zilean and now Janna are suddenly a "top pick" when they've been out of favor for such a long time
ever since I joined close to the end of Season 3, i've only ever seen scorn for those picks and have only rarely ever seen them make a significant impact on a game
Janna synergizes really well with Assassins, who're coming back into the meta following a few buffs and a nerf to exhaust.
Alistar's ultimate is basically an 8 second intervention for all the damage you'll do to him, and he still has some of the most ridiculous hard engage in the game at level two.
Zilean bullies a lot of lanes, and he can deny resets from champs like Tristana or Kha'Zix that are quite popular at the moment.
So the thing about janna is that is she is good against other support mages. While she does not heal her support kit is quite strong. Her shield at level 5 gives 50 AD plus ratio for 4 seconds. Nami's buff is only 3 autos and half the damage without any scaling.
janna fellout of favor cause of the rise of tanks which makes her life difficult in the laning phase as she is quite squishy and her CC is a windup for full cast range.
It's ADC vs Assassin meta currently.
Zilean nullifies an assassination attempt by pressing R.
Janna nullifies an assassination attempt by pressing R.
Both make their ADC demi-god's.
Alistar and Zilean also aren't going to bot lane that often. Alistar is the best turret diver in the entire game, and offers insane peel and engage.
Zilean can revive every 30 seconds meaning his ultimate is up more often than any offensive kill ultimate late game.
Team are either running an extremely glass competition without a tank, or mega-unkillable tanks. ADC's work great against both, since they two shot the glass champions, and can actually burn through the likes of Mundo, Maokai.
alistar got buffed. zilean gives a global xp boost, meaning you can get level 2 off of the first minion wave, practically guaranteeing all of your lanes get level 2 first and thus cannot fall victim to an early first blood due to a level 2 all in. His ult can also be a game changer, I honestly think it's just that the early game meta (for jg, top and mid at least) has now made him more favorable.
Janna is good with trading frequently, and her ult is great for reseting a fight. The Trading with her in Lane is probably more useful now that late game hyper carries are showing up more, as you need to beat them up early.
Middle of S2 Janna was pretty much always first picked, professionally at least. She has possibly the best peel kit in the game and a nice steroid on her shield. I think she might have been played quite a bit in SE Asia meta, but I might be wrong there.
Alistar was once a popular jungler, believe it or not, in...S2? Anyways, he received severe nerfs as a result and that gimped his support role as well. He recently got a buff and that made him a really good choice again--he's one of those champions that teeters on the edge of OP and UP as a result of the utility on his kit. His damage reduction ult allows him to build primarily damage and still serve as the team's tank, not to mention his great CC and a heal for sustain. He's mostly picked(or banned) for top I'd say, but certainly can support well (an excellent roaming support).
Zilean...ugh. He was picked in the past--primarily mid--for his ult in team fights, being great for ADC oriented comps. Since ADCs are becoming the focus for primary damage source again, I believe that's why we are seeing him more. I honestly hate seeing this champion in competitive play. His point-and-click abilities hardly require any skill and aren't in any way fun to watch be used, and he's got a BS passive that gives an EXP boost for like no reason, no effort. Janna's passive got nerfed here, why not Zilean's? I understand not every champion has to be complicated or flashy, but Zilean is just plain boring.
We are simply witnessing the ebb and flow of competitive picks. Zyra and Annie have basically disappeared from the support role despite being so popular last year at World's, and this is all due to the past year roughly of balance changes.
Games like League of Legends have many different things at play, causing different champions at any given moment to be "viable" and in the next moment not. The reverse is also true. Since the end of s3 there has been a wealth of changes that culminated in the current meta being everyone's go to picks, which is what caused various champions to be "good" again, including those that you mentioned.
Zilean has been kind of sleeper op for a while now but really gained notoriety when assassins became the norm, because he essentially neutralized at least one champion's burst
Janna suddenly burst into the scene for the same reason, and her ult is really good at peeling multiple targets off as well as completely stopping a big engage. In solo queue she is probably one of the safest/easiest champions that can ward all over the map due to her movespeed and supreme disengage
Alistar has always been good, but the change to his ult being 70% damage reduction at all ranks was huge. It allowed tower dives immediately at 6 with little to no consequence if Alistar was able to get aggro on the tower. Also his mana costs were reduced so he became a better laner. He's always been a great support, but the buffs pushed him over the top and made him a great top laner as well. This makes him a good flex pick where the opponent has to respect the fact that it may be a bot lane or a top lane Alistar. The recent nerf to not being able to punch after headbutt was huge, since that was where most if not all of his harass came from. He no longer goes top, but he might in Worlds, since they are playing on the patch before the headbutt nerf.
Previously the popular champions have been generalists that are too good at everything. Riot's been slowly weeding out these champions in favor of ones with more pronounced strengths/weaknesses, which the current Supports fit well with the current meta.
They are all anti-assassins and can protect the carries very well. They also synergize really well with their own assassins due to speed ups, shields, and revives. They bring so much utility to the teamfights. You have to remember that the LCS is nothing like solo queue.
I'm not really familiar with Janna, so no comment there.
Zilean is pretty much FotM. He doesn't offer a lot, but used right it's a game changer. His revive can completely turn around a teamfight and with his speed it makes for a great countergank. He can also splitpush really well.
Alistar has always been a strong support, not popular, but strong. And now he even got buffed. Also a lot of Alistar picks are not for support but for top.
