It is strong, especially with Frostseeker as main weapon. Then the best combo is Arcane Archer/Ascendant imo. Very high ACC, lots of crits and weapon damage->focus.
Maybe you should give Streetfighter/Helwalker a try. Dual mortars (Hand Mortar + Fire in the Hole) gives you full AoE attacks to pair with your strikes, absurd reloading speed and sneak attack bonus (the blunderbuss modal triggers the Streetfighter passive). And the absolutely best combo is AoE mortars + Stunning Surge (Monk). Also Duality of Mortal Presence (INT) is aweseome with AoE weapons and affliction durations. Dual mortar is better than rod + blast in this case because you will profit from all your Full Attacks more (two shots instead of only one).
Mirke can also use this combo, she can be a Streetfighter/Monk. No Helwalker then but that's not really important.
I highly recommend Psion/Troubadour. The following is a party build. Just make sure the Psion isn't the weakest party member in terms of deflection so he doesn't get attacked/shot at a lot:
But any caster class + Psion is great imo.
How about a Brute (Barbarian/Fighter)? This combo can have a ton of engagement slots, high health, high AR, high defenses, great self heal and at the same time attacks very quickly for a tank and does reasonable weapon damage per hit (esp. when bloodied). You can counter the deflection loss while frenzied with a large shield. Or not use frenzy as much (althoug it raises Fortitude by 20 points alone which can be very useful). Many resistances, too (Unflinching + Fighter resistances etc.) I like this as a "Mataru" Huana warrior with Kapana Taga (club), Reckless Brigandine (brigandine), Cadhu Scalth (large shield) and Death's Maw (hidden) so it looks properly like a Huana. My subclass pick would be Vanilla Barb/Unbroken (more AR with a shield) but it also works fine with both vanilla or Devoted or so.
For another look I would maybe take seomething like Gladiator Sword + Bronlar's Phalanx or so.
Rekke can be a Brute, so he can fulfill this role as well.
A Sorcerer can be a very nice healer (and much more) if you pair Livegiver(Cat form) with Bloodmage. Healing counters Blood Sacrifice's self damage. Infuse with Vital Essence makes Spiritshift and healing last longer, Cat Flurry makes you cast very fast. Spiritshift of a Livegiver grants +5 PL for all Rejuvenation spells. If Spirithift ends it's -5 PL - but you can keep up Spiritshift for a long time with Wall of Draining. This also prolongs healing and buffs on yourself, making you very tanky, too. But ofc. this is only possible at PL7:
Fassina can be a Sorcerer. She isn't a Livegiver though - but ofc. a vanilla Druid still is a great healer.
A Herald (Paladin/Chanter), especially Kind Wayfarer/Troubadour can be a great healer, too. White Flames + Exalted Endurance + Ancient Memory + Mercy and Kindness + Lay on Hands and so on makes for a great combo of passive and active healing. I actually like this best with dual pistols and not melee. It makes your positioning for White Flames less dependend on enemies' position, reloading weapons make it possible to immediately cast a healing after shooting (reloading can be canceled, unlike recovery), so it's more reactive. Pistols have a decent range unlike blunderbusses and not acc penalty (you cannot miss with White Flames else the healing doesn't happen) and you will get a Full Attacks (two shots) per FoD use which means 2*White Flames healing. It's also easy to create a custom AI setting for such a Herald since he doesn't need to move as much as a melee one.
But of course a Herald can be tanky as heck, so with a bashing shield (see Magran's Blessing for example) he can at least be a great offtank behind the brute, if not more and still proc two White Flames. Herald with Magran's Favour (Battle Axe) and Sun & Moon (Flail) can get +4 Power Level to FLames of Devotion (also raises the healing of White Flames) which would make him better at melee dmg and healing but less tanky.