For DD,most players use Klahan or A.Chancellor (any heroes with high atk power when highly transcended that have piercing,reduce buff,confirmed crit/ignore def in their skillset is viable). Veteran players mostly have those 2 heroes at max level but A.Chancellor will be easier for new/intermediate players to transcend since you can use Fina and 6* hero selector so go for it if you don't have Klahan over level 40 (bare minimum level so you can use awakening power up to reach +10).

PS:Diao-chan help with DD team survivability,one of her skill grants 6 VS to all team members (so A.Chancellor immune to magic atk only is not a problem).

For CT,Rin is not mandatory,you have other options for the main dps slot (like A.Chancellor).But CT require some special heroes/normal heroes in team composition to beat certain floors,just having a strong backline dps won't help you.You can search on Youtube for some CT teams videos for the level you are currently doing.Two sample video below.



TLDR version : Yes,A.Chancellor is a good hero for DD and most CT floors.