What really changed things were all the DD updates. That, and ToAU.
Before ToAU our exp parties were crabs and birds and ***in bibiki bay-- the mobs lasted longer than 42 seconds, and DDs weren't as buffed as they are these days.
Then 2-handed update came and spiked up the difference even more, making it more and more difficult for plds to keep hate in a purely defensive manner; then people started seeing that if they kill the mob fast enough anyone can tank, so why bother with a pld when /nin can take a few hits, and sam can virtually tank while doing 3x as much dmg as a pld or nin.
That started to force a lot of plds to try to add on DD gear so you can assimilate that atleast your doing SOME damage, and noticed that it helps keep as well <-- this was also helped by the increase in availability for DD gear (Hauby no longer costs 5 mil, you can get one for 500k or so when this movement started, and now down to less than 200k)
I find it really funny that ppl keep mentioning atonement as changing things... when I was in DD and hybrid gear for well over a year beforehand.
Anyways, once you start hitting late 50s, early 60s, its really time to start looking at some gear mixes
I found it best to have 3 sets: DD/ws gear, hybrid gear, full tank gear --- and macro between them
(I actually have ctrl lines for gear change, 3+4 into ws gear, 4+5 into DD gear, 5+6 into hybrid gear, and 6+7 into full defense... have it set so that 3 was all the ws pieces I dont wanna DD in, 5 was pieces I wanted to DD in either full DD or hybrid, 6 was shield gear; so that I could quickly switch and stuff and conserve macros (just use SE's macro book, so limited to 6 lines apiece))
then flash, provoke, cure, sentinel, rampart and (while leveling) warcry all had enmity gear macroed in beforehand; some of them I would have like... 2 macro in (warwolf and herc) the move, wait 2, and macro back out for "idling" <-- but seperate book for pure tanking that macros it all in, and have a reset macro allowing me to get back into idle gear
But however you do it, just because you may decide (and recommend it) a hybrid build, don't neglect your defensive build and keep it a macro away -- if you guys link, you can take voke/flash both keep it off mages and get into defensive gear; if you accidently pull something too tough you can take it; if a pt member dies, or half th eparty afk-- whatever the reason theres always cases where the situation changes and you might need to quickly get into turtle mode
But for the risk of sounding repeatative, in my experience... I haven't noticed any difference whatsoever between my DD and turtle sets in taking damage... I just like to have it there because the human eye cant discern it all, and if it comes down to a few points difference in life/death, feel way better about myself if I die in defensive gear, than if I was fooling around in dding gear and end up dead; but a good 90% the time I was in an exp party I was in offensive gear, and fared quite well
But basically...
#1 priority for anything is shield skill -- get yourself as much as you can, because almost all your damage mitigation is due to your shield
then you can make your builds for I would DD go with
accuracy <--- gonna need to hit for tp, and hit consistantly to make DD work
attack <-- wanna hit for more than 0 dmg, more dmg you do more enmity you get
haste <--- decrease flash timer, which helps you get hate faster, as well as hit faster for more damage over time, which is more enmity over time
strength
dex
for defensive
enmity <-- gonna need it (especially for flash/voke/cure macros)
vit
hp
def <-- somewhat effective, but best to choose pieces that have high def and other stats imo, wouldn't use it as a driving factor in choosing gear because 5 more def, but no enmity or vit isn't exactly a better piece
Then when you get to fast pts you can work on a method that works best with you, for the actual tanking part
its really effective to start rotating your abilities... 1 ja per mob unless emergency (and depending on how fast you get tp, use that ws as a "ja" or a big cure as well)
also zerk is handy, use it before your ws, then pop defender (this will bring you back to "normal"), get tp up, drop defender, ws, and drop zerk (or use it in conjunction with sentinel for extra damage as well)