The default-white Objective Marker in the 3D-view frequently gets lost in the background of the island scenery, white ground-color, waves, clouds etc. Outlining the marker might help a little, but the real fix is a color change to a high-luminance value different from the scenery. In the case of the Stratis scenery, bright YELLOW is the best choice..... but even better.. allow the player to define the color and brightness.

However, there is a problem in the ARMA3 Alpha. The InGame color choices are severely block-restricted... the Objective Marker is lumped into a single "Active Markers" color-group so that if you want to change the Objective Marker color to, say, Yellow , then for example the 'Normal' Status of the Helicopter condition flags (White) is also changed to Yellow, and the weapon cross-hair is also changed to yellow.

The Objective Marker issue is really a symptom of a bigger (but pretty easy to fix) problem in the UI Color Selections. The InGame "Active Markers" color group needs to be broken out into its logical subgroups.. status flags, aiming reticules, objective markers.. etc... with optional user-control of each subgroup color. The default for all can initially be white, of course.

Some hard facts from release 0.60 and dev release 0.61 (June 14, 2013)

ARMA3Alpha Helicopter Showcase.
1920x1080, ULTRA setting,
CPU: i7-2600K @ 4.6 GHz
SINGLE GTX780 Superclocked (Titan's not-so-baby brother on steroids), factory default (940 Base -> 1157MHz max. Boost).

FPS 25-30 when over land, ~ 50 when over sea.
PEAK GPU Core activity ONLY 54%... !!!

CPU Activity:Only ONE CPU core ~ 90%, Other 3 CPU cores LESS THAN 25% PEAK !!!

Comparison test with ARMA2OA V1.62 Helicopter and VTOL Boot camp scenarios, same hardware.
ALL graphics MAXED manually in ARMA2OA Advanced Settings.
1920x1080, FPS 70-90 over land.
GPU Core activity between 65% and 90%.

CPU Activity: TWO cores ~ 90%, other two ~ 20%.

ARMA3 is a very ambitious action game, and as a simulator requires a lot more compute resources than a typical shooter. Bohemia is putting much effort (and money, no doubt) into creating realistic scenery/objects, etc. and offering graphics options to match. However, modern graphics hardware at high graphics settings requires substantial CPU processing and data pushing to maintain the FPS essential to the real-time action elements.

If the serious under-usage of available CPU horsepower in ARMA3 V0.6x is not radically corrected in the game ENGINE before game release, then the addition of desired user-features will be continuously competing with the real-time action elements for compute resources artificially limited by the engine design.

This issue was first reported in March 2013 and "Assigned" at that time. Noting the fact than ARMA2OA V1.62 (update mid 2012) fully utilizes 2 CPU cores and runs at a comfortable >70FPS when pushed (with maxed graphics) on my hardware, I am very surprised that the ARMA3 Alpha engine 3 months after "Assignment" is still primarily using just one CPU core and has not added the full horsepower of an additional CPU core. The most modest of action-oriented PCs today all have dual-core CPU architectures as a minimum.