Alright, I've run several battles using each game mode and each deployment, though not every combination and some more than others. After the first couple I realized that the Templar had an unfair advantage points-wise. So I changed some of my Castellan's equipment and dropped the Dreadnought and Chainfists, bringing my total to 496, only 46 more than the orks. The battles continued and, as they did, I adjusted the tactics as necessary.
Now, the Templar stay back and don't charge unless to deny the enemy charging them and unload as much firepower as possible before the orks reach them. The orks, on the other hand, use the terrain better and have their Boyz run in front of their Warboss and Nobz to provide both cover and distraction. Rather than shooting at all they simply charge across the board as fast as possible so that they can get into close combat.
Surprisingly, a squad of 5 marines can hold their own in close combat with 7-8 Boyz for a few rounds. Also, the Warboss is the most devastating figure on the board. There is nothing he cannot kill aside from a full terminator squad and he even gives them a run for their money. 4 attacks at WS 5, S 10, from a power klaw is so dangerous. Fortunately if he's out in the open and I get a rapid fire off I can wound him enough to take out in close combat with a higher initiative.
Another thing I've noticed is that the only protection I get from cover is if the orks end their movement close enough to charge easily, when they shoot. I already go before them so I literally get no benefit from holding a position in cover.
I will continue to run battles and become more fluent in the rules, I've been considering switching out my Terminator squad for the Dreadnought to change things up. I also need to play on a board that is actually about 4-6 rather than 3-3.
On a side note, I have begun shopping for my Emperor's Champion and will be making a purchase in the next couple of days. When he arrives and I paint him, I'll post a update about it.