Why would it be a problem in classic? You can barely get Hive3 up in under ~10 minutes or so, and that'd probably mean you'll need two dedicated people for hiving. Add in that you'll need to hold down those 3 locations, and getting 3 hives is pretty tricky - certainly if an Alien team can get there, the effect should be similiarly strong to say getting a HA train.
Third hive should be strong, true, but it should not automatically mean the game is over. If the marines are winning the resource war they should retain a reasonable chance of winning. Doubled damage for xenocide, as with focus, would be extremely powerful, and if used well it would invariably render the game unwinnable for the marines.
You cannot truly compare a long-term investment such as a hive to a short-term investment such as a heavy armor train. The heavy armor train may be more powerful at first, but in the long run the hive is ultimately more powerful.
And Focus-Xeno would do what, kill LA marines quickly? Thats not sooooo aweful.
I certainly see it as a problem. Why should the fully upgraded base tech of one team render the fully upgraded base tech of the other team obsolete? Furthermore, the power of focused xenocide would not be limited to light marines. A single focused xenocide would inflict severe damage on even heavily armored marines.
it might be the lowest alien but it's the highest tech (without upgrades) of it. Like an LA with lvl 3 armour and weapons =P
Therefore it should be similar in strength to a fully upgraded light marine, rather than far surpassing it as it would if it could use focus with xenocide.
I'd say that's more than fair enough considering the xeno makes the skulk have to sit out for a bit after the attack... just make it xenofocus has double rein time or something ~shrugs~
The fact that xenocide kills the Skulk is largely irrelevant considering that Skulks generally die regardless of whether or not they use xenocide. Also, I doubt an additional 7 seconds spent in the spawn queue would matter. More than that might matter; however, forcing players to spend much time out of the game is not something I have any great desire to do.