Im not sure if this is intentional or if its a bug. Regardless, you cannot set down Waymarks while casting. Making it really hard to organize mid-fight.

Time: X
Frequency: Always
World name: Leviathan
Character name: Kyng Ex
NPC name: X
Monster name: X
Class/Level: Arcanist / 50
Party or solo: Both
Race: Miqo'te Male
In-game time: X
Area and coordinates: X
Steps:
1. Begin casting.
2. Attempt to set a Waymark
3. ????
4. Cry.

Connection Specs
- Type of internet connection/provider: Century Link
- Connection Speed: 40 mbps down / 5 mbps up
- Modem maker/model number: X

PC Specs
-=-=-=-=- System Information -=-=-=-=-

CPU: AMD Athlon(tm) II X2 260 Processor 3.20 GHz
4.00 GB RAM
Windows 7 Ultimate
Gygabyte GA-870A-UD3 Motherboard
Onboard Sound
NVidia Gforce GTS 450
Some cheap generic keyboard
Razer Naga Mouse

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Browser Information
- Name and version of the browser currently in-use: Google Chrome 27.0.1453.116 m
- Internet Explorer Version: X