EV training helped my fast, offensive pokes 1-2 HKO most of the late-game enemies (Although you can argue a Lucario would normally OHKO anything w/ STAB Close Combat).
If you are able to EV train, chances are that you have a pretty stable team that can cover each Pokemon's weaknesses. That's how you are able to get away with being 'squishy' and having 0 EV invested into defensive stats. Not to mention the fact that you can also have defensive pokes on your team to pivot or switch into unfavorable match ups.