The damage proc on Ludens Echo does the same amount of damage it's always done. The item even lost 10 AP. I don't think it's damage is as much of a problem as the fact that the item seems to be overloaded now, basically forcing you into buying it.
Mana, AP, Damage Proc, 20% CDR all on 1 item with a reasonable build path all for only 100 gold more than it used to be? Sounds too good to pass up imo, but I digress. The damage itself hasn't changed with the exception of the AP (-10), so unless it's a bug, it's working as intended.