Before picking the second Strategist, name what the first one already covers. Some supports stabilize chip damage well. Some stop dive. Some enable a carry angle. Some add damage when the team is healthy. If both players cover the same job, the team may still lose to the first real pressure point.
A useful duo spreads responsibility. One player can keep the frontline healthy while the other saves a control, revive, barrier, burst heal, or repositioning tool for the moment that decides the fight. That separation matters more than copying a generic best-support list.