If anything, Torchlight is to Diablo what DOTA2 is to DotA.
You understand that the Diablo 2 team from Blizzard (former division of BN) left Blizzard, worked on other projects, and eventually formed up as Runic?
The actual people that made Diablo 2 made Torchlight.
The actual people who are making Diablo 3 are part of Blizzard's WoW team...
In the same way that HoN and LoL are DotA clones, whereas DOTA2 is under the guidance of IceFrog...