What sets the massive star formation rates and efficiencies of giant
  molecular clouds?
  Galactic star formation scaling relations show increased scatter from kpc to
sub-kpc scales. Investigating this scatter may hold important clues to how the
star formation process evolves in time and space. Here, we combine different
molecular gas tracers, different star formation indicators probing distinct
populations of massive stars, and knowledge on the evolutionary state of each
star forming region to derive star formation properties of $\sim$150 star
forming complexes over the face of the Large Magellanic Cloud. We find that the
rate of massive star formation ramps up when stellar clusters emerge and boost
the formation of subsequent generations of massive stars. In addition, we
reveal that the star formation efficiency of individual GMCs declines with
increasing cloud gas mass ($M_\mathrm{cloud}$). This trend persists in Galactic
star forming regions, and implies higher molecular gas depletion times for
larger GMCs.
  We compare the star formation efficiency per freefall time
($\epsilon_\mathrm{ff}$) with predictions from various widely-used analytical
star formation models. We show that while these models can produce large
dispersions in $\epsilon_\mathrm{ff}$ similar to observations, the origin of
the model-predicted scatter is inconsistent with observations. Moreover, all
models fail to reproduce the observed decline of $\epsilon_\mathrm{ff}$ with
increasing $M_\mathrm{cloud}$ in the LMC and the Milky Way. We conclude that
analytical star formation models idealizing global turbulence levels, cloud
densities, and assuming a stationary SFR are inconsistent with observations
from modern datasets tracing massive star formation on individual cloud scales.
Instead, we reiterate the importance of local stellar feedback in shaping the
properties of GMCs and setting their massive star formation rate.
