Overview

Articuno has very solid defense, but it suffers from one of the semi-common flaws that Pokemon with good defensive stats tend to have: an Ice typing. Ice alone puts Articuno in range of a few big-name attackers, and adding Flying to it just makes things that much worse for everyone's Team Mystic mascot. A duo is very viable with a bit of careful dodging, and is even easier partly cloudy weather

Approach

Team composition

Charizard's two formes are the only currently viable Mega Evolutions for the raid, though boosting Fire Type still doesn't put it on a par with most things that are just tossing rocks.

Rampardos, Shadow Tyranitar, Rhyperior, Terrakion, and Shadow Omastar are the true VIPs of this fight

Many other Pokemon are viable, but keep in mind that even non-STAB/weak rock moves tend to be stronger here than 1x super effective, strong STAB moves.

Battling strategy

Given the right team comp, DPS is not an issue at all. A bit of dodging is needed to make the duo work in general.

Note: "Good" movesets are not necessarily viable at the level indicated.