Im  in  the  same  position  with  different  characters  so  take  with  a  grain  of  salt.  Looking  at  just  their  abilities  on  paper  you  have  a  good  arena  team  and  cb/  dragon  team  but  theyre  different  and  almost  starkly  contrasted  like  1  or  2  big  guys  in  one  are  not  great  for  the  other.  

So  the  big  names  ive  heard  thrown  about  and/  or  looked  up.  Rector,  spider,  apoth,  war  maiden,  frozen  banshee.  

wytherer  looks  great  all  around.  Leech  i  think  is  lifesteal  for  everybody,  also  has  healing  and  buff  management.  Def  a  legendary  healer.  Probably  makes  apothacary  obsolete.

gisleah  ive  geard  talk  about  maybe  just  a  recent  fusion  event.  Looks  lackluster.  Good  for  arena  but  wont  be  freezing  any  bosses  or  dragons.  Blocks  debuffs  though  so  may  use  on  dragon  just  for  that.

epics  rector  and  spider.  Rector  i  hear  talk  about.  good  and  im  scared  of  them  in  arena.  Another  good  healer  but  you  got  a  legendary  one  and  the  rest  of  us  got  apoth  so  youre  good  there.

spider,  looks  good.  A  standard  atk  and  def  debuffer same  as  warmaiden  but  epic-er.  

apoth  and  war  maiden  youve  got  better  of  unless  you  prefer  a  rare  easier  to  book  cheaper  version  of  them.  Spirit  host  is  your  speed  up  person  i  think.  Thats  where  i  got  my  early  lego for.  If  you  need  that.  Shes  not  great  at  it,  looks  like.

frozen  banshee  ive  geard  talk  of,  dont  have  one  myself.  Looks  like  a  ok  poisoner,  more  poson  booster.  They  have  to  be  under  her  debuff  and  hit  by  her.  ive  got  urtica  whos  similar  but  lets  anyone  appky  poison  under  her  debuff  and  also  has  poison  sensitivity  so  may  poison  well  tigether  but  idk  if  multiple  poison  people  takes  too  many  battle  slots.  Ive  intended  to  pair  her  with  someone  and  having  to  put  poison  gear  on  a  poisoner  seems  like  you  shouldnt  have  to.  

spider  seems  like  your  next  atk  person  after???  You  need  a  main  atacker  then  maybe  spider.  Idk  if  he can  be  it.  Wheres  your  main  champ  or  did  you  ditch  Galek?  Kael  or  athel  are  basic  nukers,  damage  dealers.  I  didnt  look  at  all  of  your  list.  

or  try  frozen  and  be  a  esrly  poison  team  but  need  a  fast  farmer  more  immediately.  If  gisleah  hits  hard  maybe  can  be  a  main  atk.  

gisleah  if  she  hits  hard  even  if  not  ideal  for  cb  or  dragon  then  spider,  wytherer,  and  can  try  out  your  4th  spot  with  speed  from spirithost,  poison,  another  main  attack  or  revive  if  wytherer  is  only  heals,  rector   if revive is  her  thing  but  sonetimes  you  want  more  atk.

The first lvl 60 champ should allways be a champ that can farm campaign 12-3 or 12-6 solo, together with 3 food champs. His job is to produce more lvl 60 champs fast.

I'm pretty sure Whythir the crowned is not a good campaign farmer, even if her A1 hits all enemies. I don't have that champ, so I'm not sure how her AI behaves, but if it's like the AI of other champs with similar skills, she probably prefers her cooldown skills over her A1. The base def and the damage multiplier are low as well, you would need incredible good damage gear (on a healer!) to make Wythir a campaign farmer that one-shots the enemy waves. That's not a good idea.

So you still need a campaign farmer as lvl 60!

I tested Sinesha in mediocre gear, she could do 12-6 in 40 seconds. Not ideal, the spirit affinity enemies result in a lot of weak hits. Zargala would have the same problem.

Do you still have your starter champ among your rares? They can farm 12-3 pretty quick and are good choices for a first (or in your case second) lvl 60.

Your  next  lvl  60  is  easy.

-  Skullcrown

Skullcrown  is  a  very  powerful  damage  dealer  /  nuker.

This  means you  will  use  her  in  every  team  you  make  for  a  very  long  time.

The  only  place  Skullcrown doesn't belong  in  is  CB

I have to agree that skullcrown is a good option. She will definately make your leveling a breeze.

Unless you have a kael that you did not mention in the rare section. Idealy you would want someone good in campaign, arena, dragon dungeon and CB. Kael fits that role. 

So go for skullcrown if you value arena and campaign times higher. Or if you have kael go for him if you value CB and dragon progress higher.