Personally I have done both and would like to point out why soloing could be good for your "class" or not.
Ignoring Zombies when there is a Scarab in the room can get you killed so it is generally best to kill everything in the room when a Scarab shows up.
Striker; you can break blocks easy and move monsters with little trouble, however when dealing with the large masses of zombies that accumulate when hunting scarabs you may want some extra firepower at your back. As a partner you want a support bomber (hazes and vortexs) or a knockback free gunner (alchemers, needle guns, and antiguas). (you can also pick a Knockback Gunner if they are good at crowd control)
(elemental brandishes, WMRH, DA, Flourish/BTB)
(you can solo but support for this class is useful)
Gunner (knockback free); you pick off monsters as you move but you probably aren't the biggest source of damage, find a striker to pair up with and if he has a support bomber try to pick a complementary status (don't bring the same one he has) to pair with his to maximize damage (fire and shock together ruin Zombies).
(Shock and fire Status alchemers, AP, Blitz and Plague needle)
Gunner (knockback); You move the masses and create paths through the horde and when a scarab is found corner it and once your striker or bomber reaches it keep the rest of the undead off your backs. (you can pair with a striker or a knockback bomber)
(Supernova, Polaris, Valiance)
Bomber Support; you need a partner, your job is to slow monsters down and slowly melt them to death, you keep the masses aggroed to you and keep them off your partner who will deal with any scarabs. (pair with anyone)
(suggested bombs: VT, AOA, EV)
Bomber knockback; a real powerhouse if you can play it, you just walk through rooms waking the undead and if a scarab shows up level the place. (the less people in your party the bigger a chunk of monster HP you can take out, percentage wise) If you do end up with a teammate be sure to tell them that you bomb with knockback bombs.
(suggested bombs: Nitronome, Deadly Crystal Shards, ITD)
(Probably the only one that makes sense to solo in)
Hybrid; as a mixed knight take your cues from the above class suggestions.
its up to you if you want to go solo or not no matter your class. when im helping friends and guildies what i do once i reach cementery it just waking up every tomb and ignoring everything, including scarabs. once i reach the elevator i just tell guildies "i got X amount of scarabs" and then invite them to the party, since monster already spawned they will have the HP of 1 player party so they can kill them easily and still get tokens from the scarabs, no matter the class you are.
at least its what i do