Titans and their AoEs have changed the battlefield of Sins that is for sure and the lighter frigates have taken a beating. That said I still think they have a place is used properly.
***Warning! This is Theory Crafting.***
Light Frigates are designed to hit Support cruisers (Cruiser Carriers, Repair Cruisers, etc) so run them on the flanks and out of range of the Titan, hitting its supporting cruisers behind it would help bring it down.
Long Range Frigates are designed to hit Light Frigates and can hit them from farther away thus acting as guards protecting the support cruisers.
Heavy Cruisers can tank the damage that LRFs can give out and rip them apart allowing LFs to get close and do their job.
Meanwhile the Titans and Capital ships duke it out amongst themselves hoping that their strike teams are effective in removing the enemies support cruisers to bring in a finally crushing blow.