So right after U24 patch notes dropped on PTS some nightblade mains are complaining about how their class identity is diminished while stamsorcs are complaining about how the skill is useless. Is this really the case? Well, let us use facts and figures to answer this question.

Skills:
Relentless Focus (I'm picking the stamina morph because we want to compare stam skills vs stam skills to lower variables associated with mag vs stam skill)
Bound Armaments (for those who don't know yet, bound armament's stamina morph is changed on PTS but not in patch notes).

Similarities:
Cost: They're both exactly the same stam cost sitting at 2295 stamina and the recast being half of initial cast.
Range: both 28 meters
Condition: both get stacks from light attacks

Differences
Now the differences are actually more striking than it seems.

Relentless Focus
Focus your senses for 30 seconds, reducing your damage taken by 2% with every Light or Heavy Attack, up to 5 times. While active, hitting an enemy with 5 Light or Heavy Attacks converts this ability into Assassin's Scourge, allowing you to fire a spectral arrow for half cost that deals XXXX Disease Damage, and heals for 33% of the damage dealt if you are within 7 meters of the enemy.

Bound Armaments
Arm yourself with the power of oblivion for 40 seconds, causing your Light and Heavy Attacks to summon a Bound Weapon for 10 seconds, up to 4 times. You can reactivate this ability for half cost to arm the weapons, causing them to strike your target for XXX physical damage every 0.3 seconds. While slotted, your maximum stamina is increased by 5% and your light attack damage is increased by 10%.

Now, we see that the two skills are actually VERY different. If you have actually tested Bound Armaments in combat on PTS you'll know what I mean. First, let us get the easy things out of the way. Relentless focus deals disease damage while bound Armaments deals physical damage. This means that grim focus can proc major defile while bound armaments can't.

Secondly, I don't have the exact formula but from wearing the same set of gear on PTS damage per light attack is higher on relentless focus than on bound armaments. For example, Relentless Focus' tool tip might read 12500 after 5 light attacks which is 2500 per light attack. Bound Armaments on the other hand reads something like 2300 per bound weapon up to 4 which is a total of 9200 damage. This is a major difference because the amount of "burst" you can get from "charging" up the skill is lower than Relentless Focus and per light attack damage is also slightly lower. This leads to the next point, Relentless Focus is a burst skill while Bound Armaments is more of a sustained DPS skill.

Why?!?!? Not only is the damage per light attack of Bound Armament lower, the maximum stack of Bound Armament only reaches 4. Furthermore, Relentless focus deals damage in a single burst projectile while Bound Armament deals damage spread across 0.9 seconds. The attack sequence looks something like: Bound Weapon => 0.3s => Bound Weapon => 0.3s => Bound Weapon => 0.3s => Bound Weapon. What bound armament does is charge up an attack every 4 light attacks so you can use it instead of your primary spammable to increase overall DPS. Relentless Focus is used as a big burst, but bound armament isn't. Due to the time it takes to deal its full 4 Bound Weapon damage, it is possible to roll dodge after seeing the first blade fly towards you and effectively mitigate the damage of the other blades. Of course, it is also possible to cast this skill while enemy is half way done with roll dodge immunity and have the final few blades hit the enemy. This makes Bound Armaments a more consistent source of damage but not a great source of burst. (Personally, I am quite excited about this because bow stamsorc for the fun!).

Because of the nature of Bound Armaments, we must also discuss the duration. Some people think that Bound Armament has a better "40 second duration". However, each bound weapon only lasts for 10 seconds. Therefore, the duration of a full 4 hit bound weapon is actually less than 40s! It does allow you to precast Bound Armament before battle much earlier, but I would definitely trade a reduction in duration of Bound Armament to 30 seconds for any other sort of small buff.

Finally, the extra bonuses for Relentless Focus and Bound Armaments are different.
Relentless focus reduces damage taken up to 10% at 5 stacks. This is actually quite a reduction in damage and is part of the reason why you're actually not shooting yourself in the leg by not firing off relentless focus as soon as you do 5 light attacks. The skill is designed for you to hold onto it a bit longer until your chance is just right. Furthermore, it heals the user for 33% of the damage dealt if you're within 7 meters. This is a very nightblade themed attack because nightblades with their more "assassin-like" feeling have the option to shoot it from afar but also attack from close distance to get the full value out of it. On the other hand, Bound Armaments is a flat increase in light attack and stamina. This, just like the skill itself, goes to show its emphasis on overall sustained DPS rather than a single burst nor does it have any condition like stacking attacks for damage reduction or distance-to-target altering the skill.

Conclusion
Bound Armament change is definitely a good and interesting one. A deeper analysis of the skills shows that Relentless Focus and Bound Armaments while they share similarities are definitely skills that serve different purposes and does not diminish the "identity" of one class due to the other class having a skill that is recastable by stacking light attacks. Sharing light attack recastable stacks is about as far as the similarities go because the two skills serve a very different purpose and provides different buffs.