If you play SAGA for any length of time you may quickly realize how powerful skill checks are when rolled against a target's Defense scores. This is because while defense scores start at 10 they often go up slowing and in small steps. On the other hand just getting trained in a skill give you a +5 modifier with that skill and then skill focus gives you another +5 modifier and these can be taken at first level. When a human Jedi 1 is rolling his UtF check with MOVE Object at a +12 bonus (assumes CHA 12) hitting a Defense score of 13 or lower is AUTOMATIC which is what causes problems. Now defense scores increase +1 per heroic level while skills only go up half that fast so at the highest levels these things are somewhat balanced but while getting there these skill checks vs defense scores can DOMINATE the game.
A common house rule to help fix the "skill check vs. defense score" problem is to introduce the Skill Attack Modifier (SAM) to the game.
The
SAM for a trained skill = level + skill's ability modifier + other modifiers to the skill with some exceptions. The primary exception is Skill Focus where its +5 modifier to the skill check is reduced to a +2 modifier to the SAM; other fixed +5 skill bonuses may get the same treatment.
Example: Human Jedi 6; CHA 14; Trained in UtF; Has Skill Focus (UtF). Skills: UtF +15; SAM: UtF +10
Example: Human Jedi 1; CHA 14; Trained in UtF; Has Skill Focus (UtF). Skills: UtF +12; SAM: UtF +5
Example: Human Jedi 16; CHA 16; Trained in UtF; Has Skill Focus (UtF). Skills: UtF +21; SAM: UtF +21
When using a skill you will still roll a single d20 just like you normally would. If the result will be checked against a target's Defense Score you add the SAM to the roll to make the comparison; if the result will be checked against anything else (usually the tables to determine effect) you use the normal skill modifier. If you would normally check the roll against both a fixed DC and a target Defense score, such as using Move Object, you will use BOTH the SAM to check against the Defense and the normal skill modifier to check against the fixed DC.
SAM and Untrained skills: There are two trains of thought here and I will present both so a GM can choose which to use.
1. Use the SAM as calculated for a trained skill but apply a -5 penalty for an untrained (non-proficient) skill.
2. Just use the skill modifier as you normally would.
Option 1 punishes an character for trying to use a skill untrained when it targets a DEFENSE score. This make skill training a lot more important for anything which may target a defense score.
Option 2 avoids the massive problems normally cause by stacking +5 from skill focus with the +5 bonus for having a skill trained. Here you are using the skill like the RAW describes and some skills are still useful untrained against some DEF scores. Using this means that a trained skill doesn't have much of an advantage over an untrained skill at the lower levels but it will grow as the levels start adding up.
Now I may be missing some things so if anyone has something to add just go for it.
Here's another writeup I found in WotC community pages.
http://community.wizards.com/pukunui/blog/2011/03/23/skill_attack_modifier