Guild Wars 2

You can only stack one sigil at a time. The second one will never stack untill you max out the 1st one to 25.

If you look up sigils on the wiki, it list all of the sigils, it explains this. It also explains what other sigils do not work in direct conjunction to one another.

As coglin said
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Vague rules of efficiency of sigils:

• Do not use two “on crit” sigils in two hands
• Do not use two “on weaponswap” sigils in two hands
• Do not use one “on crit” and one “on weaponswap” in two different weaponsets
• Do not use different “kill stack” sigils in any weapons

Nretep.2564:

• Do not use one “on crit” and one “on weaponswap” in two different weaponsets*

why? o_O

Shirk.6421:

Nretep.2564:

• Do not use one “on crit” and one “on weaponswap” in two different weaponsets*

why? o_O

Because of the cooldown timers.

If Set 1 has an on-crit sigil on it and Set 2 has a weaponswap sigil, what you end up with is this:

• If Set 1 triggers the on-crit sigil, that’ll put the weaponswap Sigil on Set 2 on cooldown
• If Set 2 triggers the on swap sigil, that’ll put the on-crit Sigil on Set 1 on cooldown

Basically resulting in a lot of situations where one of your sigils won’t trigger because the other already put them both on cooldown.

Holy moly, that’s the reason, I always wondered why it happens sometimes but didn’t think about this reason, but shouldn’t it be considered as a bug?

coglin.1867:

You can only stack one sigil at a time. The second one will never stack untill you max out the 1st one to 25.

If you look up sigils on the wiki, it list all of the sigils, it explains this. It also explains what other sigils do not work in direct conjunction to one another.

This is wrong. You can never (and have never been able to) gain +250 power and +250 precision by killing 50 foes.

If you have two different stat gains on your weapons then only the one on your main hand (or which ever was applied first in case of one being on different weapon sets) will apply. If you have two of the same stat gaining sigil (one on main, one of off hand) then you will gain two charges per kill.

On-kill sigils

On-kill stacking attribute bonuses remain even after you swap or unequip weapons; the stacks only end on being downed or defeated, or by traveling to another zone or instance.
If you have an “on-kill sigil” on both main-hand and off-hand weapons, only the sigil on the main-hand weapon will trigger, since that sigil takes priority and forces a cooldown on the other.
Two different on-kill stacking sigils will not provide bonuses to two different attributes. Whichever sigil triggered the first time will continue to add to its stack. (i.e. you can only have one “on kill” stacking effect active at a time). However, if you have the same on-kill stacking sigil on both main- and off-hand weapons, stacks will accumulate twice as quickly. The 25 stack limit still applies.
The same limitation applies to mixing on-kill stacking and delayed effect sigils. Only the first effect will be present.

Shirk.6421:

Holy moly, that’s the reason, I always wondered why it happens sometimes but didn’t think about this reason, but shouldn’t it be considered as a bug?

It’s been reported a billion times and a dev has mentioned it around one time but did not refer to it as a bug.

The new sigil of torment is an exemption to the shared timer though. It is an on crit but apparently it doesn’t share the timer with other sigils.