Guild Wars 2

Just make them give the whole thing at once and permanent, in the end one always ends up getting 25 stack anyway. Changing maps resets the stack and one has to start all over again, so please just make it a flat attribute.

Except then..
Bloodlust would completely outclass Force,
Perception would completely outclass Accuracy,
Corruption would completely outclass Bursting.

At 25 stacks, they already do ( usually, and usually at a little less than 25 stacks).
The whole reason you need to build those stacks is the trade off between having the benefit immediately available, or having to build stacks.

ex: accuracy sigil gives 7% crit chance, flat.
Perception gives 10 precision per stack. 21 precision = 1% crit chance.
7 × 21 = 147, or 15 stacks on a perception sigil. AKA 15+ stacks of perception > accuracy sigil.