You bring up Titan EX - may I ask you about Shinryu, bot EX and NM? Because thats the more recent primal here and you know what? People complained that that one was to difficult - and certainly not killed by a PUG-group within 40 minutes. So... have you killed that one as easly?
To be honest: I havent tried Byakko EX yet, but I'd be fine with an EX-fight thats a bit easier than Shinryu was.

You should also notice that the difficulty-mode we ditched since Ifrit, Garuda and Titan is the 4-man-mode, not the EX-mode.

Titan EX was a real nice female dog of a fight - for me at least aswell. But do you know why later EX-modes feel easier? Because we got better at the game, because we've been playing it for years. Oh and because we've got less lag now... again, I cant talk about Byakko or about the experience of anyone else, so I'll speak in general about mine: Back in 2.2 I had trouble getting out of an AoE, partly because of lag, partly because I was just to stupid to do it. Splitting up the boss in T1 and moving it across the battlefield was a challenge and I honestly believed I'd never be able to play anything but a tank during Titan-fights (since as tank you can just stand there and get your head beaten in). Today, I can solo that fight. Landslides arent an issue anymore and I use Tempered Will not to save my ass because I cant do a mechanic but to be able to ignore this wind-knockback-thing in Shinryu so I can dish out more damage.
Titan EX wasnt more difficult as a fight by itself - if we'd get that one today, it would be among the easier ones. Titan EX was bad because we were bad (and probably because of no saftey-net for getting knocked off, I'd like to have that back...).
I understand wanting to have that feeling again and a real challenge for yourself, but I'm not sure thats really possible - and if I think about how the battle with Titan was a battle with a boss, serious lack of skill and lag, I dont think I actually want that back...
Strictly mechanically speaking every EX-mode in HW and SB is more complexe than Titan EX is, as a fight.