Let me try to summarize why, despite having 160 on-paper DPS, you may be having trouble with Dagan. For reference, I just did the arc solo on two different toons (with just around a million SP each) this past weekend: I used an Incursus with 3 blasters and 1 faction drone on one toon and a rocket Corax on the other. And in spite of the triglavians infesting some of the later areas of the arc and a handful of lowsec smartbomb gate camps, they both survived relatively unharmed.
There are two problems I see with your approach, the first of which is that you forget that you’re sometimes combining offensive methods (e.g. drones plus railguns), and in those cases the on-paper DPS reflects the combined DPS of both methods, which are not always focused on the same target (therefore your DPS is in fact split, for instance when you send your drones after Dagan’s escort while you maintain fire on Dagan himself).
The second problem is that EVE employs a physics system that you didn’t understand. Some people have touched on it here, but since you’re flying Gallente it seems, let me explain via railguns/blasters: railguns are a long-range offensive option, but their tracking (i.e. their ability to continue landing hits on moving targets) is weaker than blasters, and if you get in point-blank range with railguns you run a high risk of missing most of your shots; blasters, on the other hand, are the short-range offensive weapon, and their tracking is far superior to railguns - but if you are unable to keep your target within a certain range your blasters will start missing their shots and/or doing less damage. Missiles and rockets don’t have the tracking problem (missiles are long-range, rockets short-range), and they don’t use capacitor to fire, but there is a delay between when you fire and when they deal damage (and they have their own physics related to blast radius and blast expansion speed that partially determines how much damage they actually do), and in some cases your target can move out of your missile/rocket range after you’ve fired them.
That’s about as concise an explanation as I can get. I suspect that in order to defeat Dagan, you are going to have to find a way to combine your offensive methods (if you’re still flying Gallente ships, you’re likely going to combine drones with standard firepower). Honestly if you’re going to use the Algos I’d recommend getting in close (orbit at 500m) and fire away using blasters with antimatter ammunition. Your drones can take care of Dagan’s escort, and once that’s done you can send them after Dagan as well in order to apply your ship’s full DPS to Dagan (if your blaster-only DPS is less than 100, it might be wiser to just orbit Dagan at 500m, don’t fire, and let your drones take out the escort, then start firing on Dagan when you can concentrate both your blasters and drones on him - his guns have trouble tracking targets that orbit at that range, so in spite of his target painting he is not likely to do you much damage before you start firing back).
I’ll post my two toons’ ship fits (which they used for the entire arc) in a subsequent post.