If you want to pull aggro everything you need is Pelta 3.
Templar
Battle Orders isn’t good enough to justify 1 class circle for it. It has 60 sec cooldown and lasts only 9 sec at lvl 5. Templar 1 isn’t recommended unless you really want to plant Dilgele in your guild hangout.
Corsair
Corsair goes against the concept of Peltasta 3 / Murmillo. Corsairs need 1h wep + dagger or pistol to be able to use their skills (Hexen and Dust Devil). Your best damage skills from Peltasta & Murmi are Umbo Thrust, Butterfly, Scutum Hit and Headbutt. From those, only Headbutt can be used without a shield.
You can either: Focus on Corsair, and ditch Pelta 3 / Murmi for something else (i.e. Pelta 2).
Or: Focus on Pelta 3 / Murmi and ditch Corsair.
If you want an aggro build, I would suggest the latter.
Murmillo
Shield Train isn’t a good skill. It doesn’t group up mobs as well as you’d expect (in fact, it’s terrible at doing so). It also has too much cooldown for it’s terrible damage and lack of overheats. It’s fun, but not really useful.
Murmi 2 is good for Sprint skill (which I love) and 2x AoE ratio on Scutum (which you wouldn’t be using if you went Corsair).
Suggestion
My suggestion is to build your murmi around the usual rodelero / hoplite / peltasta / shinobi classes. You can make almost any combination of those classes and still perform very well in PvE.
With the upcoming change to shinobi, I would also strongly suggest you consider adding shinobi. I’m not a big fan of shinobi myself but the class is becoming way too strong to pass up on.