What does an Epic represent for your team?
From the conversations I've had, for most software teams, epic basically equals to a feature they are building. It's broken down to user stories and tasks. I'm curious to know if you use an Epic to represent something else within your software team?
We use the term "theme" rather than "epic" but it's in the same ballpark in terms of "thing used to gather issues together". However, we don't use them to represent features, instead we use them to represent initiatives or goals. We try to work in a way that we're focused on the outcome (what does doing this work accomplish for our users) rather than the output (which features are we going to ship). This in turn means that a theme is not done when the code is completed. Instead we need to follow up on metrics, feedback, etc. and ensure that we got the outcome we were after.
Disclosure: I'm the founder of kitemaker.co, an issue tracker that is quite focused on themes and trying to help teams improve.
For us, an epic is a unit of related work which is usually sized for completion in under a quarter or two. Many epics may be completed to get through an initiative. Ex: initiative may be “make a new service to replace section $FOO of a monolith.” If this is able to be done in a quarter or so, then it is the epic. If it is larger, we may break it up into milestone epics like prototype, beta release, full release, and clean up. Like you say epics will be composed of stories, tasks, and spikes (investigations).
The desired goal of the client, which is then broken down into features and tasks.
e.g.
Epic -> "We want to georeference imagery in ${app}"
Feature1 -> Upload Imagery to app
Feature2 -> Manipulate imagery that is visible on the map with the mouse cursor
FeatureX -> ...
TaskY -> Warp an image via canvas
TaskZ -> ...
My work involves integrating financial institutions with our tech. In our workflow, each Epic corresponds to one institution.