If I have two things that activate at the beginning of the end step, what happens?
Unfortunately, you don't get the servo.

Hidden Stockpile has an "intervening if" trigger, which means it checks the state to see if it even goes on the stack.  If a creature had not left before the end step, then it won't ever go on the stack.


  603.4. A triggered ability may read “When/Whenever/At [trigger event], if [condition], [effect].” When the trigger event occurs, the ability checks whether the stated condition is true. The ability triggers only if it is; otherwise it does nothing. If the ability triggers, it checks the stated condition again as it resolves. If the condition isn’t true at that time, the ability is removed from the stack and does nothing. Note that this mirrors the check for legal targets. This rule is referred to as the “intervening ‘if’ clause” rule. (The word “if” has only its normal English meaning anywhere else in the text of a card; this rule only applies to an “if” that immediately follows a trigger condition.)