Chillblaze, I have to contradict.
You are right with research dragons, but you can also have purple other buffs when you have the research bonus.
We are talking about purple passiv skills. They affect all your units, in wall and mainarmy.
What means that they are also good even when you start a new account for your wall, siege or events.
And if you are ahead with other players (even on an new server) the active bonuses (mostly the last..) can be usefull in pvp, since dragons have also stats and help outstatting others.