Basically I'm looking for a weapon what will be the most effective for your average slayer task. Is the rapier still the best option or had EoC changed that?

I honestly have no looked as to whether Kuradal assigns more slash or stab monsters. If she assigns more slash monsters, I personally would go with the CLS. If she doesn't, just get the rapier.

Looks about even.

 

 

Aberrant Spectres - Thrown

Abyssal Demons - Slash

Aquanites - Arrows

Black Demons - Bolts

Black Dragons - Arrows

Bloodvelds - Fire spells

Blue Dragons - Arrows

Dagannoths - Air spells

Dark Beasts - Bolts

Desert Strykwyrms - Stab

Dust Devils - Crush

Fire Giants - Slash

Ganodermic Beasts - Fire Spells

Gargoyles - Water spells

Greater Demons - Bolts

Grotworms - Bolts

Hellhounds - Slash

Ice Strykwyrms - Fire spells

Iron Dragons - Water spells

Jungle Strykwyrms - Stab

Kalphites - Water spells

Living Rock Creatures - Crush

Mithril Dragons - Earth spells

Mutated Jadinkos - Stab

Nerchyael - Crush

Skeletal Wyverns - Fire spells

Spiritual Mages - Bolts

Steel Dragons - Water spells

Suqahs - Fire spells

Terror Dogs - Slash

Tzhaar - Use combat triangle logic

Vyrewatch - Thrown

Warped Tortoises - Bolts

Waterfiends - Bolts

 

Aren't Jadinkos, Jungle Strykewyrms and Desert Strykewyrms all skip tasks though?

Go with the maul. Duel wield is vastly under-powered compared to 2H(Plus you need 300k tokens for MH+OH). And plus, you can maul pretty much any melee-weak task with only a 15% accuracy penalty(Or better yet just get a Z spear and BGS).

Considering the only Chaotic 2h weapon are either the staff or maul, your choice of either. I'd choose Maul because the T75 substitute is more expensive for Crush than Magic (1.6M vs 400k). 1h weapons are only really better if you boss or if you use momentum and DW, which for the case of latter, you need both MH and OH.