Is a designated anti trojan program really needed?

I dont see too much of a need for an AT software, an AV product is sufficient for most people, but we all know no AV is 100% effective, so an additional form of protection does help (just encase anything squeezes through).
I use 1 AV (which includes HIPS method of protection) and 2 AS products (for on-demand scans) and do a online scan (using Web-AV scanners) if anything gets through.

Need Layered protection with different branded products, don't rely on one solution, always keep a backup scanner (AV, AS or AT)