I'm going to preface this, by saying 2/6 missions in the generals handbook require either wizards, or heros with artifacts to score objectives. Places of Arcane Power, for example, will be very hard for you to win, as you have only one artifact in your army.
I know you play in a fairly competitive group, so my advice will be based on that.
First, I suggest you buy the getting started
book for Age of Sigmar. It's $10cnd, and includes a Knight Incantor (probably a $30-$40 model). This is a wizard, who can once per game automatically dispel any spell. I think the inclusion of this model would be very valuable for your army, and will give you the ability to handle endless spells and also gets you a wizard to capture objectives with.
He's 140pts, so I think that's fairly comparable with the Navigator, or can replace the Endrinmaster if you have a spare couple of points.
So, Overlords are the sort of army, where in a 5 round tourniment you'll expect (with practice and a good list), go 3/5. Their units sort of don't have a lot of variety, so you will find situations you will struggle with.
The common way for overlords to do well, is the 'Clown Car' list, where you take the Barak in which you can deepstrike one of your ships, load as many units as you can into it, deepstrike and charge out of it Turn 1.
With Command points allowing re-roll charges, and the Endrinriggers having fly (so they can fly over chaff walls), that's probably your best bet. I'd probably put as many Endrinriggers into one unit, to make most benifit of the command re-roll for charges.
I think the rest of the list is fine. There are not really any bad units in KO, but they are fairly expensive, and the Company are equiped just as I would run them.
I think the main thing, is playing games and figuring out which ship to drop, what to put inside and knowing where to drop it, to unload your murder balloons.