Not your fault, sounds more like your ISP having routing issues to SE, or else everyone who plays FFXIV would have the same problem.
SE even stated that the main problem is routing issues from some ISPs, especially within Europe. Main point is though, it's silly to blame latency in this day and age in regards to Ifrit, which is why some people will flatout dismiss it because it was an old excuse from people who did suck at the fight.
Can it be a problem? Sure if you have bad enough connection to SE it can be, but in general? Not to the point it will make or break your battle.
