All the generals have great responses to this. Oak's shield, Sedna's heal, and QoT's brambles can all block or negate a coordinated snipe. All these abilities can target a friendly demigod and can be used to interrupted this combo quite effectively. Erebus can also turn into mist form to avoid this concentrated fire if he anticipates it.
I think it's the assassins that have trouble, and in fact I've found the assassins to be very lacking when the other team has a coordinated strategy since none of them have any defensive abilities at all. Once they get to high levels and have good equipment that's another story, but early game it's quite a problem. Healing potions would be a very good idea.
You have to be very cautious, but one of the upshots is that any Regulus snipe build is going to have very weak combat abilities. In a straight on fight, he's going to lose, so if you are careful and don't feed they'll have a lot of trouble keeping flags, which gives you a substantial long-term advantage.
you cant beat it... a full regulus team (as long as skill levels are the same, and they are not retarded to stand still) can block any attempt to rush like nothing else can.
mines are so fucking imba... cost efficient, "instant" high area damage spike, 8 sec cd and slow effect...
a general build is just useless, getting high lvl creeps just makes it worse since they clear up a gigant in 1 skill... the only demigod that could actually kill a regulus is probably UB, but I just DARE you to try get close once they get mines lvl 4.
Dont wanna get close? theill just snipe the fuck out of you...
PLUS try to ignore one and he can push any tower in a few seconds without even taking damage.
so wanna beat regulus team? go play ctf and full cap loc