I usually give Roald strength gear so he can focus on attacking while I give Veradux Vitality gear, so he can survive multiple hits and still heal everyone as needed.
I give Roald full Str equipment, because all his attacks depend on strength. the damage of the fire attacks also increase with more str so i guess it depends on str.
as for veradux i prefer a balance between instinct and vitality for his healing abilities, electro bolt and his survival. veradux hardly uses electro bolt while attacking and uses more of melee attacks so I think it would be better if you didn't use him for offence at all. however he recovers 40 focus with one of the melee strikes :P maybe important for long battles
for Felicity I use full Str gear, because her default equips that give piercing usually give really low str and vit...that would make her very fragile. also i find that her normal hits on STR gear match the damage of her critical hits with piercing gear.
None of the equipment will mess up their attack patterns. If you use your teammates offensively, give them equipment with more strength, speed, or piercing. If you use them as healers, then you should give them stuff with more instinct.
Also, recycle your old equipment before selling it, it might be right for your team mates.
I gave roald nigh vision,flex-o-matic,black-ops boots,darkfiber leggings,black-ops uniform(still looking for good weapon), and to veradux I gave android armor,cyborg legging(also looking for weapon,boots,head,gloves)