I do have to agree - there is alot more balancing work needed for PvP. We been concentrating on patches and new content too much, in April we plan several patches that will specifically adjust balancing in PvP.
There is one more thing I should have mentioned. Getting the Dragon healed is only time-efficient at NPC town - healing merchant. And healing a badly damaged Dragon costs around 2,000 in gold - so that player pays as much as you would to get your army to full strength.
Also - can you please clarify what you mean about getting a Dragon being too easy? 60-120 influence is rather hard to come by.
The units you are giving as counter are weak against anything else than dragons.
Not really - somehow they are underused, but if used right these units are not only Dragon slayers.
Units such as Mounted Knights or Mounted Grand Masters actually overpower almost everything in-game.
And Halberdier, Impaler, Sentry units can devastate cavalry as well as monster units and any even archers if used in loose formation.