I remember the only time the characters were seen was at the "Disney Electrical Parade" which ran there until 2010. The characters did start showing up more often once DCA got a new look around 2012.
This is categorically false. Disney characters appeared in the park from day 1 in various meet-n-greets, they just weren't involved in the entertainment at first (they weren't in the parade, etc.). The fab five were in Sun Plaza, Kuzco, Kronk, Quasi and Esmeralda were in Hollywood Backlot, Chip, Dale, Pooh, et al were in Grizzly Peak, etc.
By June 2001, mini character shows had been added throughout the park (Max joined LaFeet, the bizarre painting Donald show in Grizzly Peak, the Farmer Mickey show in particular was absolutely painful). The Electrical Parade came in July 2001, adding a major show with characters as there were none at the time - Eureka and Steps In Time were character-free. Goofy's Beach Party Bash replaced Lights Camera Chaos! relatively quickly (can't remember exactly when), and by 2005 Block Party Bash brought a daytime character parade to the park three years after Eureka disappeared.
It was originally the plan to not have characters in the park, but that was canned and reversed before the park ever opened to guests.
All that to say, DCA was full of characters well before 2012.