I suggest you use the dread drake flame guard, life drain and a pet aviar and fight with skull knight. The result will be skull knight keep getting stun and silence. Assume your daddy skull knight didn't use talent Iron will and pet ruduff.
First of all i should tell you the only heroes that worth to upgrade by order: lavanic,zephyrica,reaper,dovekeeper,anubis,occultist,skeletica,rosaleen,cosmo,bogeyman,lazulix,wallawalla and hardly gunslinger Any other hero is not worth your time and resources.
From two heros you mentioned about two years ago skull night still was useful but now people only maxing alot of skull knights just for raising their mights otherwise it's completely useless but dread dreak with maxed out revive and unholypact still used for guild wars so clearly DD is more useful.
Woah, DD is not an obsolete hero at all. I'm in #2 guild and most of my guildmates, including myself, all use DD in GW attacks. He is amazing at clearing bases. Use revive 9/up9, and just wait until all troops are dead, then drop him away from stun hero's and towers, and he will get 3 volleys off and clear over %50 of the base most of the time.