from what i've heard
fire, SS and Stone are strong DPS secondaries
but i dont know much, you should wait for more feedback ^^
if you want to softcap without IO sets, you'll probably want the fighting pool for Weave and chose the SuperJump travel power with Combat jumping (+def(all))
my two cents 
With your stipulations I'm gonna say firemelee hands down. It's probably still right near the top even with major inf dumped into the build.
No build for you, but shield powers+2 slotted cj+weave+steadfast 3% def should get you to about 43% def. I'm sure you can squeeze out the last bit in w/e way you like.
I agree that /Fire has the most DPS, as it usually does, but /Stone is fun as hell. Lots of knockup/knockdown, not to mention Heavy Mallet & Seismic Smash are really heavy hitters. And Shield Smash goes quite well with the other knockup/knockdown powers like Fault & Tremor.
I am fairly well impressed with my Shield/Electric Melee tanker's damage output at level 30, and think she'll be a beast by 39. It isn't any one attack that makes the set, but the multi target output is easily the best of any tanker secondary I've seen, and the endurance efficiency seems reasonable so far as well, partly because your attacks can return endurance to you. Of the five damage dealing attacks I plan to take on the tanker, four of them have some kind of multi-target capacity. The set is rather slow, and you may eventually want Hasten, though.
If your ambition is to solo archvillains, forget this and go Shield/Dark Melee. If you plan on mowing down several spawns at once and working the Roman wall, go Shield/Electric. I haven't gotten mine to that point yet, but I suspect it will work well there.
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"At what point do we say, 'You're mucking with our myths'?" - Harlan Ellison
I have a level-bumped 50 Shield/Electric on Test from closed beta and even on SO's it's a beast; I've been sorely tempted to roll one on Live. On the other hand I have a mid-20's Shield/Fire that is just starting to really shine; I'll probably end up taking him to 50 before rolling another shield tank.
I've really been sold on Shield ever since my BS/Shield scrapper got to around 35; at 50 it's almost as durable as my Invuln tanker. Naturally it took a sizeable IO investment to get to that level... around $150 million as I recall.
On the other hand I should be able to soft cap my shield tanker for very little, opening up the build for other IO bonuses. Hmm, I really have way too many alts and thanks to issue 16 I end up playing 50's more than anything else now.
COH has just been murdered by NCSoft. http://www.change.org/petitions/ncso...city-of-heroes
I'm making a shield tank, but the rest is up in the air. I'm trying to maximize my DPS. The only limits I have are:
I realize by not using sets I'm already limiting myself a good deal, but I want a budget build. I can always invest more influence later.
Tanks are new to me. Given these limitations, what is my best choice for a high-DPS secondary? And example builds or suggestions on powers would be appreciated. Thanks!