If you don't play competitively, you should try. It's really not as hard as you would think, and it really does bring more life into the games. I've been competitive for three years and I'm happy I did it.
I'm honestly not that familiar with Latias, to be honest. I never used it in the months that it was OU, and whenever it was used against me I honestly didn't have much trouble with it because I love to run banded Careful specially defensive Tyranitar, which is basically BUILT to kill Latias. But Latias is amazing at sweeping, and support, so I understand why it went to Ubers. It was just dominating the metagame.
Salamence, if you ask me, is more of a threat than Latias. At least with Latias you know she's going to hit you from the special side. With Salamence it's a completely different story. Something is going to get hit hard, or he's going to be able to set up before you know the set, and by then it's too late a lot of the time. Salamence is extremely unpredictable and therefore doesn't truly have a counter. Even though Choice Band Scizor can deal with it alright after Stealth Rock and one turn of Life Orb damage.
EVing is really confusing and frustrating if you don't know what you're doing. But after you do it for long enough you get it down to a neat little system. I just breed, IV check, level them up, de-EV them, vitamins, infect with Pokerus, EV train. Of course it helps if you have the Power Items, which turns one Bidoof into 10 HP EVs and makes it much, much faster. IVs are more frustrating since you can't control them as easily. I don't exactly breed for IVs, simply because I'm lazy. Though I'd like to teach myself how. I simply breed six of the same thing, same natures and all that, and IV check those. So at least there's a little bit of control with that.
Overall, Pokesav = Must have.