I'm talking the original bosses that it took a group of 40 top geared players AT LEAST 10-20 attempt to take them down and never succeed. Like the dragons that used to spawn in Duskwood. Ugh those dragons. Lethon was always the hardest. Rarely would a group take him down. Then there was Emeriss, Ysondre and Taerar. I really miss these old world boss. Deep down I hope in Legion and being in the Emerald Dream we'll see Lethon again. I hated him but loved him the time.
Oh. And the original Zaricotl (when he was red) and was the bane of anyone questing in the Badlands. Gaw. Another beast I hated and loved all at the same time. I swear Blizz put him there purely to troll and kill players. I think his original level was like 55 too! I wish he kept his original look too.
For the entire time that I could get xp from Barrens, I leveled there with my dwarf hunter. There was a rare pet or two there that I really wanted. I learned exactly where I needed to go in Ratchet for the guards to protect me.
Eyes of the beast was great. Using it hoping to learn the rank of the spell faster of the pet you just tamed (and had to give up a slot for) wasn't. Running out of ammo (and wasting a whole bag for it) wasn't great either. Weapon training was kind of interesting, I had everything I could level up to max, including throwing, but excluding bows and crossbows (both at zero).