As boardroom tussles go, activist Elliott Investment Management’s campaign at RWE looks relatively collegial. The UK arm of the U.S. activist investor on Monday disclosed a 5% stake in the 24-billion-euro German energy giant, and cheered its recent decision to scale back capital expenditures while nudging CEO Markus Krebber towards bigger share buybacks. The only room for disagreement seems to be on the timing, which gets at a more fundamental problem for European bosses: how much store to set in a nascent public and private investment boom?