I don't see much synergy between Earth and Rad, but the combo surely is godly. As an Earth/Rad you'll have the tools to control several mobs without any issues (and at range).
Salt Crystals... I hate it. It could be handy if it were ranged, but it's a PbAoE. IMO, totally skippable. About look of it.. You see those CoT crystals? Well, Salt Crystals are similar but in white. Each foe gets locked into each one of those crystals. It looks good but the only reason I would pick it is for IO set bonuses.
*Edit*
Grab stamina so you can use all your awesome control potential non-stop and shine in teams.
@False Fiction - Virtue / Defiant
Current projects - [Glaciologist - Ill/Cold Troller] [Cloudshaper - Storm/Dark Def] [Harald Wartooth - Elec/Psi Domi]
I would say that if you are using your toggles a lot you would still need stamina unless you pick up some +recovery set bonuses or a unique IO. Perhaps something to respec into later?
I agree with F_F on the Salt Crystals and I would only take one of the immobilizes depending on play style. Everything else in the primary is worth taking IMO.
Earth/ is also a set that benefits greatly from Hasten imo as you have several medium and long recharging powers.
Being able yo stick your placeable powers down around corners can make life much easier than many other controller sets 
Octavian Vanguard
@ohmsEU and @ohms 2
Badging character: Bimble on the Union server, Badgehunter.com and City Info Tracker.
Thanks for the advice. Got up to level 7 last night, so methinks I'll be snagging something besides Salt Crystals in a few bars...like Hasten. I'll also most likely snag stamina as you say, just wasn't sure if Accelerated Metabolism was helpful in that regard. My Mind/Psy Dom did just fine Stamina-free to where he sits at level 37, but without the Domination inherent and not being sure how Drain Psyche compares to AM, Stamina's probably a good bet.
Oh and False, you're totally right, I totally misused the word synergy. I think I just meant "overkill". All the Earth power basics give a -20% defense buff...combined with the 1st Rad Toggle means anything that gets hit has a nice -45% Debuff that's only going to get worse as things stack.
Quicksand & Lingering Radiation both look to do the same thing so I'm expecting them to grind things to a halt...and Volcanic Gases & Choking Cloud do similar things....
Yeah, you're description sounds about right. No synergy, just lots of ranged control.
Thanks again guys and if anyone can vouch for Accelerated Metabolism or not, let me know. Lord knows I don't have the slots to waste if it's a lost cause.
-jared
Quicksand got a base 25&DefDebuff too IIRC. I skipped Chocking Cloud because, as I said, I play mostly at range.
You can skip Stamina if you combine a few uniques and some purple sets (think all purple sets give you 4%EndRec at 2nd IO). I prefer recharge bonus on my Earth/Rad tho.
@False Fiction - Virtue / Defiant
Current projects - [Glaciologist - Ill/Cold Troller] [Cloudshaper - Storm/Dark Def] [Harald Wartooth - Elec/Psi Domi]
I would keep Stamina: AM gives you a nice +30% recov unslotted (better than Stamina), but won't be anywhere near perma until you have lots of +rechg bonuses (get Hasten soon anyway). I don't think that the synergy between the 2 sets is bad though, although there is admittedly a bit of overlap: for example QS and LR both have -mvt but the first also has -jmp/fly and -def while LR has -regen and -rechg. CC I would skip with all the control you have (and skip Crystals too). With Stalagmites + Stone Cages at low levels along with your hold and QS, then EQ and your rad debuffs, and finally VG, Stoney and EMP: overall Earth/Rad is a very nice combo 
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CoX 50s: <ill/rad> <ice/ice> <fire/kin> <grav/sonic> <ice/storm> <earth/kin> <kin/elec> <cold/psy> <thugs/dark> <fire/dark> <dark/elec> <night widow> <EM/ninj> <mind/icy>
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I would keep Stamina: AM gives you a nice +30% recov unslotted (better than Stamina), but won't be anywhere near perma until you have lots of +rechg bonuses (get Hasten soon anyway). I don't think that the synergy between the 2 sets is bad though, although there is admittedly a bit of overlap: for example QS and LR both have -mvt but the first also has -jmp/fly and -def while LR has -regen and -rechg. CC I would skip with all the control you have (and skip Crystals too). With Stalagmites + Stone Cages at low levels along with your hold and QS, then EQ and your rad debuffs, and finally VG, Stoney and EMP: overall Earth/Rad is a very nice combo .
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Was going to say what Okton said on the stamina issue. Another great thing is that with hasten and AM, there is very little AM downtime if you activate them one after the other and with a few +recharge bonuses perma AM is easily achievable
Ok. So I finally got my 1st Blaster on Heroes to the "golden" level (that's the level where I have the powers that make him fun and all the rest are gravy on top of the rest) so it's time for me to try out another archetype. Since my Villain love was Domination, I figured I'd give their blue cousins a try.
I like my toons to have a little synergy between their Power Sets and I guess I wanted a veteran's or just a regular Controller player's advice. What I plan on rolling this afternoon is an Earth Control/Radiation character. Now my question is are the synergies worth it? I'm sure the Radiation Infection/Any Earth Control Power debuff combo isn't an issue, but I don't know what debuff caps are but I do know that the combined slows from Quicksand + Lingering Radiation might hit it. Maybe. I don't know.
General advice would be great, particularly on this combination.
Other questions: Would a 6-slotted Accelerated Metabolism (3 End Mod, 3 Recharge) make my need for Stamina negligible?
I know that there are....issues...with Salt Crystals, but does anyone have a Screenshot of what that looks like? I know it's pretty iffy to have on a team, but the description tempts me beyond words.
Thanks!
-Jared