Like coloneh said, dervish is pretty self sufficient. It meshes pretty badly with secondaries.
I initially went warrior just for wild blow. Scythes have the highest crit in the game, and the dervish has no stance enders themselves. Distracting blow can get handy if you absolutely need an interrupt.
Monk for healing is not that hot since you have plenty of healing and protection in earth prayers and mysticism. Tho hex removal is handy since a dervish only has some pretty awkward options for doing that himself; one of them is elite, and one is in wind prayers which is mostly the pvp/utility line. Dervs also have no condition removal.
Other than that, I can't really think of anything that synergizes well in general. There might be that odd assassin skill, a couple of necro skills, but overall you will be using 100% dervish skills for most of the time, and only switch secondary when you absolutely need that one or two certain skills from another prof.
As for own/suck, here's imo:
I'm a religious [wiki]armor of sanctity[/wiki] user. It's basically shielding hands 24/7. It casts fast and has a 5e cost. I usually use it together with [wiki]aura of thorns[/wiki].
[wiki]heart of fury[/wiki] is one of the better IAS'es in the game for the sheer fact of having a decent duration, being in a line which you'll already probably be using, and being completely unconditional. The burning at the end helps to nudge you over if you're juuuust this close to killing something.
[wiki]ebon dust aura[/wiki] for utter melee/ranger 24/7 shutdown. Can even be kept up for bosses since you'll be constantly applying and re-applying it. Note it only triggers on an attack skill, and not an attack.
[wiki]mystic sweep[/wiki] and [wiki]eremite's attack[/wiki] are some commonly used skills in damage builds, as they are the only dervish attacks with a 3/4 cast time. You can queue these up after a regular default attack for basically a double hit. Works great together with [wiki]avatar of lyssa[/wiki] since it gives you the chance to actively try and catch skill activations.
If you like avatars, [wiki]eternal aura[/wiki] is a near must-have pve skill. It's the only possible way to keep avatars up 24/7.
Dervish has a lot of "lose one enchantment" skills, but don't shun them thinking "well I want my enchantments!". Keep in mind that you *want* to end some enchantments (like aura of thorns), and you can also end enchantments as they are about to end anyway. Like with armor of sanctity and mystic regeneration, these have fairly fast recharges, so you can "afford" to end them prematurely if you really have to, and they will always be guaranteed recharged if they are blinking.
Some skills I (and many others) have yet to see the real use for. Feel free to play around with them and prove us wrong.
[wiki]sand shards[/wiki], even tho it triggers once for every foe you miss, the damage is just so low and the criteria is just so situational that this skill only allows you to deal a tiny amount of damage for a few seconds every 3 hours.
[wiki]vow of piety[/wiki], only real use I can think of would be if you had one or two monks spamming reversal on you. Even then, you have no control over what it heals, making it rather novelty based. It's cheap and fast to cast/recharge, but if you want a dummy/cover enchantment, there are better options.
[wiki]Test of faith[/wiki], sounds really good on paper, but if you manage to get a monster or player down to half health, do you really *need* to remove his enchants in the first place? Slow recharge and high'ish energy cost to make the damage desirable.
[wiki]irresistible sweep[/wiki], if blocking is a problem, I'll bring wild blow or [wiki]guiding hands[/wiki]. If I'm making a build where I want to rend my own enchants, I'd rather bring [wiki]eremite's zeal[/wiki], [wiki]meditation[/wiki], [wiki]twin moon sweep[/wiki], or [wiki]signet of pious light[/wiki]. I just personally don't see the use in rending an enchant and spending a skillslot just for *one* hit that would otherwise miss.
[wiki]grenth's grasp[/wiki], it's a good skill, but with [wiki]harrier's grasp[/wiki] it's not really needed. The only difference is that you get to cripple foes standing still. Which you can also just do with [wiki]crippling sweep[/wiki] and [wiki]aura of thorns[/wiki]. Also plus points for allowing you to spam cripple I guess, but I've never found a practical use for it where harrier's grasp couldn't do the job just as well.
More than that and I'd start moving into purely opinion matter I think. I think I covered most of the commonly agreed upon stuff.
my first char is a derv lol. Now your new best mates are enchantments