Let me start off by agreeing with:
First some general advice.
Having multiple options available (multiple ascended heroes) will increase the effectiveness of your gameplay. Finishing events, special quests, winning raids and war battles and scoring well in titan fights all depend on what heroes you take into the fight.
When I realised this I made the decision not to ascend any 5* heroes before I had my bench of 3* and a couple of 4* heroes ready to fight with. I would only ascend a 5* hero if I did not have another choice or if the 5* hero would be an awesome addition.
An example: the only 5* hero i brought to 2/60 early on was Aeron, because I lacked another healer besides Belith and Hawkmoon.
Some good advice on how to progress effeciently. That being said; let’s look at your list.
For now I would upgrade Misandra to 3-70 and focus on ascending Kiril to 4/80. Besides his healing ability he also increases your attack and defense, which is useful for both defending and attacking.
As you do not have another 4* green hero, go with Melendor. You’ll have two available healers then; Kiril and Melendor.
Gormek, Grimm and Tiburtus (Wilbur) are necessary heroes for your attacking team, because they lower the defense of 3 targets. This boosts your next special attacks and tile hits with a significant amount! Finish Tiburtus first, then Rigard.
I’m no big fan of any 4* yellow, except Wu Kong. Li Xiu is a fine mid-tier hero for defense teams. Continue to ascend him.
You do not have a red 4* hero, so I would use the red feeders along with the blue feeders on Misandra right now. Speed up her progress and work on Kiril.
Tyrum, Balthazar, Mnesseus and Friar Tuck are three 3* heroes I would also ascend. Pretty useful for events. So will be Belith, Brienne, Berden as green heroes.
Ideally you want your strongest heroes here with special skills, which compliment each other. Also a rainbow team pays off better in most cases.
I would not yield a rainbow defense team with your current set of heroes, because you lack a 4* red hero. I would try for now:
Kiril - Tiburtus - Li Xiu - Little John (or Melendor) - Misandra
Or yield 2 purples as flank:
Misandra - Tiburtus - Li Xiu - Rigard - Little John