You should take a look at this thread:

https://plarium.com/forum/en/raid-shadow-legends/674_game-discussion/615424_solo-farming-with-ninja--for-trips-and-krama-especially-d/

I love the build that Harlequinn posted. It's really not that hard to reach those stats. You have Ninja, so if you can build that, you can solo farm dragon 20.

But, if that is out of reach, your dragon 20 team could easily be:

• Martyr lead (safety net) 
• Ninja (wave control)
• Frozen Banshee (boss killer)
• Zargala (wave clearer)
• Gorgorab (TM boost, healing, ATK up)

For  a  Dragon  team-  there  are  quite  a  few  core  parts  that  you'll  need.

First  you'll  need  a  poisoner.  I'd  say  Frozen  Banshee,  as  she  is  already  leveled  and  probably  (hopefully)  geared  well.  For  different  affinities,  you  may  need  to  use  someone  else,  like  Aothar  or  Occult  Brawler,  but  FB  is  fine  on  Stage  20.

Next  you  need  someone  to  speed  up  the  waves,  a  Drop  Defense  champion.  I  see  three  in  your  roster,  Spider  is  who  I  would  recommend.  He's  also  killing  multiple  birds  with  one  stone,  bringing  attack  down  and  weaken  as  well.  I  would  also  recommend  him  as  your  next  60.

You'll  also  need  some  sort  of  sustain.  Who  better  than  Scyl?  She'll  also  bring  you  crowd  control  as  well  as  heal  +  revive.

With  all  thaf  out  of  the  way,  you  could  throw  Ninja  into  the  mix,  bringing  crowd  control  so  hopefully  your  enemies  never  get  a  turn  as  well  as  MORE  damage.

Lastly,  you  probably  just  want  to  speed  up  your  run,  so  I'd  throw  Royal  Guard  in  there  for  his  massive  slam  speeding  up  waves  and  dragon  alike.

I added Gorgorab to my team.  I can clear Dragon 20 in 2:30.  Its not a solution, its a patch.  You get to harvest better gear for your other champs so you can retire Gorgorab.  

Gorgorab can 100% be part of a stable/reasonably quick Dragon 20 team for a long time. He brings quite a lot to the table. it will be account dependent, of course. 

Love the ninja build but not there yet.

will try some of these suggestions decided to 60 Gorgorab as he does help alot in the contect I play. May not be the best one to do at this time but time will tell.

Excellent choice