Will any of these champs be seeing a rework/overhaul in the future?
The new mage update might hurt his ability to harass with his Q since mana regen has been cut for just flat out more mana. Also many of the items he tends to use like ROA, need to stack up for the good stats or are very expensive. But that isn't the only reason I am asking. He has become stale and outdated IMO. Even his ult, which was the main reason to play Karthus, is less effective now that many new/reworked champs can save you, themselves or both from the damage. Champions like 
all can save at least one team member and in the case of and , the full team is a possibility. Karthus also has no solid form of CC. His W is not great as it is directions, and is just a slow, not a stun or root. Lastly he is not a solid counter to anyone.
I find it hard to see a match-up where singed is the best choice. The Proxy Farming King, is a mild nuisance at best and his only redeeming trait is how fast he can split push. His poison trail is ok, as long as the enemy team doesn't know to you shouldn't walk in it. But who doesn't know that already? Now I have yet to see what he is like after the mage update since many items now give mana. It just seems that his overall gameplay is a bit lacking at the moment.
I only see Galio in URF. Only. He has a difficult build path being that he has to get MR for his passive to function. But with AD champs dominating in the mid lane, AND with him being one of the only melee mages in the game who isn't an assassin, he struggles in most mid-lane trades since he either just takes the free poke or he chunks his mana pool.
Her strength use to be more powerful when 
were not the only ward option in the shop. That and 
now make her stealthy ganking and her seemingly "universal" presence (because you could never really know if she was ganking you or not, until the last second, because normal wards didn't work on her. but now her stealthy aspect is more of an annoyance for her to work with. Wards now being built into a jungle item make discovering where she is easy, just ward a camp or two and she pops right up when she takes it. Pinks are cheaper too. Sweepers and oracles now reveal hidden champions, even in brush with a red fill so danger brush traps are less common.
Farm to level 6 and try and ult someone. Pre-6 he probably is one of the worst gankers in the game. Post 6 he is average at best. His E makes it counter productive to gank a low health champ since they will be notified of your presence before you even be in range to damage them. Making that nice movement speed buff kinda useless when jungling while looking for ganks, at least, from what I've noticed while playing him (which isn't a lot I admit). He also can only damage 1 target, while most other junglers have some form of AOE damaging or AOE CC ability WW's real strength is in prolonged fights, but with those being less and less common due to meta's leaning heavily towards the AD assassin/ Marksmen and less towards bruiser / AP mage. WW loves 
. And the buff is gonna help a lot. But where AD is more likely in game than AP is, Armor is the better option for defense but wont help with his healing potential. Giving his early game a hard choice of do I want better healing while being weak against AD, or Build towards the meta but lose healing strengths and be weak to AP (who are the easier targets to gank being in the mid lane, but also have the least impact on a game's outcome when compered to an ADC or a strong TOP. Also, 
being a good item for ADC's while not breaking a build path, his ult is less effective.
These are just my thoughts. And are solely based on my experience with the game.
