You're welcome. There's a lot of things to think about in the load screen and champ select itself.
I'm probably missing a few things, but this is what I see, again not trying to bash on anyone (and I won't be touching on playstyle at all or anything like that, just what I see from match history):
Leona has no flash or exhaust, there is no exhaust on the team at all - therefore your damage is never going to be hindered by a summoner, however they do have a fair amount more sustain in bottom lane and Leona did bring TP, allowing her to keep up that great lane presence we love her for so you have to respect that increased early pressure. Also Lux has no flash and has chosen instead to bring Clarity (LOL why?) and Heal - no flash here either. That's two people who have no escape due to immobility and absolutely no way to flash engage on you, both of which are skillshot reliant and so these two aren't going to be your problem at all. What you'll want to be looking at instead is the WW with TP/ult map pressure, making sure to have your support pick up an early sweeper to clear out a river ward when WW is going to be looking for a play at lvl 6. You have to assume Sejuani is going to go full tank and seeing their team, you'd want to rush BoRK as your plan A.
But ruunan's is core on Kalista, I MUST HAVE IT FIRST
I hate this statement. Above all else, I hate this concept that core items > building smart. Ruunan's is a great buy, especially on Kalista when it scales so well with her passive and is quite gold efficient - yes. However the only way that team gets any tankier is if they had a Swain mid and Zac top, you're really looking at a huge frontline with decent hard engage. Burning through those champions isn't going to be an option as all 3 can lock you down, BoRK first buy.
To further enforce that, Sejuani was the first to get fed on the enemy team, picking up 4 kills by 16:30.
Why
?
% health damage is going to be instrumental vs that heavy engage frontline they have. If you were on Vayne or Kog'Maw, this wouldn't be as much of a rush as it's already built into your kit. You want to be closing out the weaknesses your champion has before capitalizing on their strengths, however this item also synergizes extremely well with Kalista - gives her everything you could ever want. A slow active, % health damage, fair amounts of AS and AD along with the almighty sustain.
After having been fed early, I'd have rushed
before anyone can stack armor to really get the most out of the low armor on champions with only 5k or so available gold to them to spend up to that point.
From there, you're looking at a highly dominant teamfight phase in the mid-game transition already without the need of
, can instead go for more damage with
or
(this is entirely choice, I know quite a few people hate IE on Kalista and would prefer the extra sustain) followed by any of the following:
(if chose IE)
(at this point, you're already pretty fed, Tristana's way behind you on CS and kills, isn't a huge threat - this is your choice)
You're sitting at 5 items, now you can look at a defensive. GA is always a good pick if you find yourself being melted with ultimates, though my preference given that only one of them is point and click CC (
) I'd opt for a
. This not only gives you MR towards Sejuani and Lux as well as Warwick's Q, but also gives you the almighty passive blocking a single spell (which we hope will be CC)
That's personally how I would've played out the game. Hope it helped with a little more insight into it.
Also I would've suggested Thresh buy an MR item rather than stacking armor with Sunfire where neither AD damage threats are even remotely fed, let alone up to par with your team - I mean, the dude was 600g behind WW as a support.
Also don't forget to upgrade your trinket. 250G is worth it after using it 3 times for a vision ward if you go that route!