First off, I'd like to say that this looks like fairly good changes for a start, and if they don't change anymore at least it won't be a completely trap option for the new player anymore (I've heard tales of woe of many first time players coming from dnd 5e trying to create their gish).
However, I'd like to examine why hybrid builds fail in ddo (I can think of only a handful of hybrid builds that have been successful in entire history of ddo post levelcap 20; as of now, there are none that are viable).
What do I define as a hybrid build: a build that tries to combine two or more offensive combat styles on a single build (melee + ranged, melee + off casting, ranged + off casting, etc.).
There are a few reasons why builds like this fail, historically in ddo:
- Gearing requirements - this is probably one of the most egregious problems at the moment. The number of effects on gear has skyrocketed in terms of what you need to minmax a style since the levelcap was at 20. The last few gearing/loot passes we've had has seen a dramatic uptick in the number of effects. Between melee power, doublestrike, deadly, insightful deadly, sneak attack, insightful sneak attack, insightful doublestrike, armor piercing, accuracy, ability score increases, etc. and the list just keeps on going on and on, you have major problem fitting in all the effects into a single styled build like assassin much less a hybrid build. Now you add on to the fact that you only get one sentient weapon which means you are going to be down some effects in both styles or down a lot of effects in one style - this can't be overlooked.
- Multiplication by 2 of requirements - when you have a hybrid build the gearing requirements, feat requirements, etc. are drastically increased (in most cases roughly multiplied by a factor of 2). If the gearing requirements weren't bad enough, try fitting in the feats you need, as well as, the destiny and scion feats to maintain two of spell power + dcs, melee power, and ranged power. Not to mention the fact that most builds (especially pure builds) have access to at most one hybrid tree. Let's take a look at sorc: savant + EK or EK + universal are really your only options. Let's take a look at ranger: DWS (hybrid tree) + AA or DWS + Tempest. You are also constrained in your enhancements that you use.
- Lack of a good hybrid epic destiny (LD at one point in time was good enough for a few melee + ranged builds to exist using old mechanics). The problem is that LD (and on a few builds FotW) are so far ahead of their counterparts that you can't really function as a melee without being in one of those two destinies (and in most cases its LD). But LD provides absolutely no benefit to your spellpower, dcs, etc. For a hybrid build your best bet probably lies with Divine Crusader, a destiny that is woefully underpowered for non-magical dps compared to LD as well as plagued with quite a few build breaking bugs. If you were to optimize for spell casting you'd either go with exalted angel, shiradi, or DI - of which none of them provide meaningful boosts to your melee ability. Worse to this you have to worry about twists of fate, as you get the same number of fate points, have access to the same number of fate slots, meaning you will end up at a deficit on something. This means that you are effectively hamstrung and unable to pick a viable ED as there are none for this hybrid combat style.
- Lack of Synergy - there just hasn't been any abilities or design work that has gone into making synergy in the combat styles to eliminate any of the other problems detailed in this post. For instance, including an ability which modulated your spellpower by a function of your melee power, would go a long way in eliminating quite a few of the above problems.
- Lack of Compensation for Additional Constraints - when you restrict something (either by proxy or directly), it will become a less valuable / less powerful choice if you don't compensate that restriction with additional power/value. It is a pretty basic tenant of game design. All of the above aside from lack of synergy, represent restrictions or constraints on hybrid builds. You need to adjust the power that these hybrid builds have by compensating them for this restriction, otherwise you'll end up with a suboptimal build choice. The important distinction here is that the compensation needs to be appropriate for the restrictions you are levying; historically this is ultimately where most hybrid builds die, there just isn't enough power compensation for the suboptimal build optimization that it requires.
In the proposal, you have gone in a direction which isn't entirely bad. You've recognized that the above are largely problems but you've failed to pull out the major tools in your toolkit to really solve it and make EK the first in a long while of hybrid builds. You've taken half measures on a lot of things: including int/cha to hit but not to damage (completely redundant because you force pdk or harper, which means nobody will take this ability), including significant power compensations in T5s roughly equivalent to stand alone T5s in the non-hybrid trees (e.g. crit range and spell crit chance, crit multi and dcs) but adding in additional restrictions, tying a lot of build strength to the capstone and eldritch strike ability but having a low uptime on it, etc..
I've spreadsheeted and run some monte carlo simulations for this build using a wizard chasis, and I've got to say it is still FAR behind its pure counterparts. I'd suggest including int/cha to damage, allowing all effects that currently scale with spell power to also be effected by melee power, having some way to cut down gearing requirements by granting melee power for spell power or vice versa, remove the ranged restriction on Knight's Transformation, half the cooldown for eldritch tempest, increase stacking size of force's point to 15, change synergistic magic from melee power/ranged power addon to haste boost, alter improved offhand's orb effect to double or triple the USP provided, and maybe include in the T5 a way to convert DCs to exceptional deadly or something.
One final note: the Knight's Transformation reads as an effect that the devs think is a good design decision but from a player pov, it reads not only as an unfun railroading ability, but more importantly as a restriction rather than a power boost. There's already significant motivation (carrot) to being in the epic defensive stance, you don't need to gate a significant chunk of EK's power behind the same casting restrictions as the stance (you see this as synergy between the two but players will see this as you motivating them with a stick).
Tl;dr: succeeds in eliminating the noob trap, but fails to really solve the problems of hybrid builds in today's ddo