what can he do Morg doesnt do better? Or anivia?
Swains vamp is on his ult. Morgs is on everything.
His aoe root is ok. but the damage vs cooldown and its delay is questionable.
a 1second delay with 2 second root. 240 damage scaling at .7ap. 125 radius. 900 range 18-10s cd.
Brands pof. .75s delay. 255 damage, .6ap scaling. and 250 radius. (+25% damage to blazed targets) 900 range. 10s cd
cho's rupture. .625s delay. 305 damage with 1ap scaling. 175 radius. 1s knockup AND 60% slow for 3s. 925 range. 9s cd (Rupture is kindof op.)
At rank 1, nevermore is complete trash. Rank 5 and with alot of AP its.. ok. But not really comparable to other ap AOE's. Anivia, cass Nami, lux? Nami's wins too. Lux's lucent singularity is about on par for damage/cd. and slow is weaker then root. so there, nevermore is probably better then lucent singularity. iceball wins. and cass's miasma is probably too different to really compare. if they stand it in, its stronger, if they don't weaker. but it also sets up twin fang of course.
His Q and E are both single target. 625 range.
A full duration Q only scales at .9. which is kindof bad considering you can just walk out of it. 255 full duration .9full duration. slow. 625 cast. 900 range for effect.
Morgs Q dark binding is 300 damage, .9AP scaling, and 1300 range. Does require line of sight to hit.
Torment I think is the worst. Mediocre 4s dot. that increases swains damage to a single target by 20% Brand, Leblanc, and xeranth have stuns from chaining spells. This thing on a 10s CD in no way comes close to kill secure those stuns do. it even only has a 625 range. Why? It should chain targets on death, and/or have a huge range imho.
Ravenous flock. sustained aoe damage at point blank. 75% spell vamp. This is.. ok. A karthus, anivia, and cass can all shell out a ton of sustained aoe damage. And with the proliferation of spell vamp in the game, its easier for them to do that as well.
All 4 have been hugely buffed by the +mana items. Chalice was kindof secretly OP, BEFORE athene's was added. Now that it upgrades into an AP/CDR item. wow.
Morg's ult is faily comparable as well. While not sustained. she can run in. ult hit all 5 champs with heavy damage. then if she lives for 3s another huge damage burst, and a 1.5s stun. His is only 3 targets. hers all 5 potentially.
his is 50/70/90 +.2 ap/s.
hers is 175/250/325 +.7ap. and again at the end.
so hers does more damage instantly, then his will do over 3 seconds. 150/210/270 and .6ap so her ult is FAR more powerful in team fights. its more damage, it slows, its all 5 champs, and can stun.
His ult is what, a farming tool? If nevermore wasn't such a pos, he wouldn't need his ult to farm.
He is a damage over time champ with little CC. That really has little place in the League. no burst, no CC, no range. while there are other champs that have those things, AND the same sustain, dot.
I don't find swain all that great when comparing to others.
If I wanted a champ with an aoe sustain ult. I would take anivia. because she also has a stun on call. higher aoe damage. And higher burst.
The entire package is morg.
Cass and xerath have more aoe, and more range. cass can cast forever.
brand, viegar, etc are better bursters.
I play Swain alot and imo he is underrated. I can tell some of what you are saying here is misguided since you compare Swain to Cass, Anivia, Xerath, Karthus, LB, Brand, etc. Swain is incredibly strong in 1 or 2 particular play styles but kinda mediocre in most others and it sounds like you either discount those play styles or just didn't account for them. Also, saying Swain has little CC is just flat-out wrong. The way you succeed with Swain is by building him as a sustain bruiser. In my opinion he is one of the best AP mids at peeling for the adc and killing other bruisers. Diving into the enemy back line to kill their carries can be done but, as you pointed out, mage assassins are better suited to this. Swain should be on the back line or in between the front line and the adc poking with his E + Q combo and CC'ing tanks and anti-carries with Q + W.
Q is a 4 second slow and with 40% cdr it's cool down is 4.8 seconds. The damage is meh until you max your E but a 40% slow on short cooldown is incredibly good cc, especially when you have a Jax, Xin, Udyr,etc. going full bore at your adc. Also, Q makes landing W much easier.
W is Swain's way to clear minion waves and it's kinda inefficient. But even at level 4-5, landing a W usually means an easy kill in lane because it generally means your target is taking full dmg from Q and from your auto attacks. Much like Cho'gath's Q, you can CC an entire enemy team with it for an effective disengage, respectable but not spectacular aoe dmg, or to peel for the adc.
E (along with his ult) is Swain's bread and butter. First, the base damage at rank 5 is 235 (compare to Annie's Q at 245) and it has a .8 ratio (compare to Annie's Q at .7). This spell is just plain good. It hits hard and it increases all your damage by 20% including damage from items and summoner spells which is HUGE. This means that ignite, DFG, Liandry's, and your auto attacks get a 20% increase in damage as well.
R is pretty straight forward: it's an aoe dot that has 75% spell vamp built into it. It also counts as 3 single target spells for items like Rylai's and the red boots upgrade.
Swain's strength is that his strength stays hidden through most of the game. But even so, a 5 item late game swain carries games hard and if needed, Swain's E + Q + W + ignite will 100-0 an adc with a BT/BoTRK just like a full LeBlanc combo. RoA + Athene's or Archangels is his core build. I will often build all 3 but after that, Liandry's provides a huge damage spike (especially late game), and Zonya's lets you tank more since your ult continues to heal you through the duration. Once or twice I've built a wota and a Spirit Visage and it made me effectively invincible. I 1v3'd three level 18s, killed one and disengaged without dying then, without recalling to base (hai2u Athene's passive) I 1v4'd while my team was doing baron and tanked 2 rounds of cooldowns without dying before my team showed up and aced them (iirc my build was boots, RoA, Athenes, Archangels, Wota, Spirit Visage). There is no way Morgana or Anivia could do that.