I always start with (Battle shout) charge -> MS -> rend -> CS -> MS -> OP -> OP (t13 2 set usually allows me to hit 2x HS inside the first CS duration since double OP's are cheap) -> MS -> (normal priority from now on). This allows me to get 3 stacks of slaughter faster than hitting rend and CS first.
Since you have apparatus, try to macro it to Deadly Calm (DC) along with blood fury. They all have similar cd's so they work fine together - that way just don't use DC before you get 5 stacks for your trinket, what might be soon as you get that 3 stacks of slaughter, or not, depending on critting RNG... And also wait/pray/time for CS before you waste it! Obviously you should dump rage closer to 0 when you plan hitting DC on.
Since everything inside DC is free, it's advised to keep HS on cooldown along with normal rotation, and save recklessness either on the execute phase or if the fight is long enough, use it early after DC - When you're still close to 100 rage and CS procs, what allows you to do nice burst with CS -> MS -> Slam -> Slam > MS rotation (plus 1-2 HS's asap if the CS won't proc again in middle of the first one so you can't extend it to be whole 12s duration spam). This is easier to do with t13 4 set with higher chance to get CS up from MS obviously, so when you don't have 4 set and the fight is under 5mins just save it for the execute.
Sweeping strikes (SS) also can be more devastating if you can align it to be used with DC, so you get nice burst to 2 targets with unlimited rage. Since SS just copies the dmg from your primary target, you should make sure CS is up on the target you're hitting at!
Other than that, the stable dps with arms comes from
hitting your abilities to cd ASAP so you won't have much idle time and you won't delay your main abilities and try to use most colossus procs as the burst window. You just have to practise for it and you'll get it in time for sure. Cooldowns are just more harder to be used efficiently