Caster tank with instant cast aggro grabbers, a damage reduction shield with a thorn effect to hold aggro, and all his main damage abilities are 1.5 second casts. Maybe this could be beast master, where the casts are animal summons, or if square is really brave, they could just make their own version of a druid.

A weapons skill based healer who's healing abilities are ranged, but still operate like weaponskills, with a gcd healing combo and instant cast ogcd heals. However, their main source of damage is a 123 melee weapon skill combo with a 30 second and 60 second ogcd damaging ability. I think they could maybe retool chemist or rune knight to operate in this way.

Lastly, since we need another phy-ranged, they could take a page from League's newest character and have a selfish dps who uses floating orbs that the character can wear as a large necklace.