Well first you have to figure out what rules you're operating under. The ADX is mainly based on domestic rules.
You have to take the worst case during the time period. Your first example splits two time periods. The first thirty minutes of the one hour before your ETA includes 1 thousand BKN so you need an alternate.
In your second example, the weather wizards think sometime between 9 and 13 the vis will be 2 miles. You can't say when that'll be so again you have to plan on the worst case and file and fuel for an alternate.