hmm..I dont see any mentions about One Man Army in the latest patch. They left it untouched, the talent works the same like previous patches , bonus applies on all characters.
The bonus only applies to characters who have the talent.
And I personally think it should be single-person talent, but not limit you from taking AI companions because AI companions are where a lot of fluff and such comes from for this game.
It otherwise should just work how it does now (Big ol' boosts to one character) on JUST one character, and go down in power if other PLAYERS are in. Because solo is still harder than multiplayer even with a 'full party'.