i've been a lux and shyvana main since i started playing in s3
i've been with them when they were great, and when they were not so great.
i can tell you exactly when the ratios of opness shifted for both of these champion's if you'd really like it know
before sated devourer shyvana was completely fine. you either went devourer/wriggles(pre-feral flare) for damage, or you went juggernaut or spirit of the ancient golem for tanky build. dps build has specific drawbacks, like being squishy as hell late game. tank build had its drawbacks because you seriously just stood there and ate damage, while doing very little of your own.
suddenly
come out and all of that gets turned on its head.
now shyvana can rush a sated fairly quickly, build a titanic hydra, and then continue to build extremely tanky while dishing out massive damage.
was perfectly fine before mage item changes and pre-detonation on her e
she was safe, had solid damage if you could keep up with your opposing laner, and had some pretty good utility late game.
then blizz- (sorry i'm used to blizzard making retarded decisions like this) RIOT broke mage itemization to the point where very few mages can use them effectively or safely. meanwhile assassins, biggest mage counter, saw new itemization changes thanks to marksman/bruiser changes.
suddenly half of the mages in the game aren't viable anymore, and lux is only considered viable because of her massive range.
then there's the new easily abused keystone talents that come out that push lux even further over the edge.
now, because riot completely changed the game from the ground up(again for the 3rd straight season in terms of itemization) people are screaming for shyvana's and lux's heads.
what people don't realize, is the exact same thing happened to
5-12 months ago.
by that i mean sion, sej, rek, and morde were all crushing at one point due to bogus OP itemization, got subsequently nerfed into the ground for it, and then never got compensation buffs after said op itemization finally got brought down a peg. leaving these champs to kind of rot in the dust.
please riot, stop looking at champions to nerf, and start looking at bogus itemization that crowds out all variety because of how easily abused it is.
Tl:DR 90% of gameplay forums is a bunch of morons who just look for "X CHAMPION IS OP PLS NERF" when really it's just 5 or 6 items that are completely broken, breaking anyone who can abuse it.