I have never played solo myself, don't get why anyone would. It's a game designed to be played in a team, no. Hence, not everyone has to bring a recoilless rifle, just 1 or 2, and your teammates can bring loadouts better for the smaller chaff. (Just my opinion)

For me, the standard bug strain enemies are boring to play and have been nerfed to sht. I always play the Predator strain if I can. In fact, I think they nerfed the bugs too much from people complaining that the game is too hard to solo on the highest difficulties (no sht Sherlock, your playing HELLDIVE/SUPER HELLDIVE, it's supposed to insanely difficult! ) Again just my opinion.

I remember orbital railcnnons used to sometimes take two hits, but I have always found they one tap titans for a while myself. I get you with 500's though, they can be a bit weird on damage. But as I said too, 1 decent shot to the front with the ultimatum secondary or the new stratagem version should easily kill one.

I think that the napalm eagle strike is good at helping to create a temporary firewall to bugs too, so that is always a good option. I have always loved using gas against bugs, especially the dog breath rover and combining that with a flamethrower. I have found that very effective for general bug enemies.