I have never gotten a full bar in 30 dragons full pt or not. I also seem to get more light per hour farming Anubis than I do dragons. Idk what ppl have with dragons but the light they give me is minimal at best compared to other sources when you consider the amount of light per hour. When I was a fresh 35 I joined an Anubis box farm and got so much light I was honestly perplexed why ppl kept saying it took so long.

After the flowers pt above I joined a dragon farm pt just because I wanted to compare and after 90 minutes of constant back and forth with them I still hadn't even gotten a single full bar and that even includes the light from the cow nm that spawned nearby. From my exp When you kill dragons or elementals on the 5s and 10s they seem to give a nice jump in light more often than not while spamming just the dragons themselves give tiny little slivers every now and then.