Been playing about a week now, Solo'ed BOLand SM; I'm really enjoying the game; but I have found the mobs way more passive than I'm used to, Like you can bomb a mob in a line or group and they toon right next to him will not respond at all. Im more used to aggro chaining especially in dungeons.
I assume as one gets closer to Lv 65 the mobs get alot more aggressive? but it would be nice to know that for sure.
At 65, dungeons are more based on bosses so there are little to no mobs. Except for dungeons such as Kalivan's Dreadnaught/Kalivan's Challenge, those do have mobs and they will chain in groups. Depending on your use on the word aggressive, they are very strong but easy to kill like normal.
Like most MMO'S the mobs have an aggro range, you may have just been out of that range. In most dungeons you can chain mobs pretty easily.
Hmmm, there's a type of mobs that sometimes does that. Some world bosses will "call" the mobs around it when you get aggro, the first one youl find to do such things is Kulsilva (lvl 18-ish) in Oblivion Woods, but they nerfed the guy hard, so a player on the same level won't really need to worry about it.
It isn't very common either, but some BAMs also have little minions that work as an "alarm system": if you hit it, the BAM will go after you. Currently I think only teraliths in Blessing Basin and magmaras in Ex-Prima do that.