When playing a reaver, the flex line really doesn't have a good anytime style other than Diamondback (taunt) or Python (30 str debuff). I often use Python first vs melees for the 30 str debuff but then after that, should I be using Diamondback as an anytime or just waiting for reactives on parry/block? Of course I'm slamming and using Leviathan when possible but after stun wears off or has been purged I want to make sure I'm maximizing my DPS.
You don't really use anytimes with the reaver. Made it to RR9 (15 years ago, mostly duoing) without even having it on my quickbar. You get a lot of parries and blocks with a reaver and the chains are long enough that by the time you finish one, you already have another block or parry. Bear in mind, this was with a buff bot back then so you might not have quite the same dex level and thus, same rate of parries/blocks.
I don't know how good the reaver is with just the potions now but other than a heavy tank, I would be able to kill or almost kill every other class with slam + leviathan (3 or 4 if you're lucky) before the stun wears off. If they survive the slam then they should be pretty much almost dead so it doesn't matter much to max the dps. If you aren't getting off 3 leviathan per slam you should be getting a faster whip and getting as much quickness as you can (again, might not be possible to get 3 leviathans in without buffs).
In the scenario where they purge, you have enough survivability to last till the stun immunity wears off where you then proceed to slam and kill them. Just engage if things get dicey. My biggest issue back then was dual wielding light tanks that purged (other than OP post-patch thanes and valks) because it'd be hard to get a block off but with the changes on this server where dual wielding is only a 25% penalty to block opposed to 50%, you shouldn't have any problems with light tanks.
When playing a reaver, the flex line really doesn't have a good anytime style other than Diamondback (taunt) or Python (30 str debuff). I often use Python first vs melees for the 30 str debuff but then after that, should I be using Diamondback as an anytime or just waiting for reactives on parry/block? Of course I'm slamming and using Leviathan when possible but after stun wears off or has been purged I want to make sure I'm maximizing my DPS.
I don't know if python is really worth it. Even though it delves for 30str debuff. In practice it only debuffs 15 strength. At least during testing in duels.
The other thing to try and practice is levi-ing with run throughs. It can be tough to pull off, especially if your opponent is also doing it. Though if your opponent is also trying to do run throughs, trying to get your side style off is usually easier.