can I switch out my reflect gear for other equips (Sheep Hat to Abysmal Knight Helm) without breaking their focus at me?
Yes you most definitely can and that would be the most recommended way to tank MVPs, whether with hat switching for shield switching.
Needless to say, the safest would to have the reflective gear equipped on always to really ensure that MVP keeps it focus on you, so if you can tank it fine with only reflective gears then I'd say just do so.
If tanking harder MVPs that you need your reduction gears then yeah, switch to keep your party safe!
However, always be tentative when you switch out your reflective gear after laying a few reflected hits on the MVP, make sure that you do not get knocked back (either MVP don't have the skills to / you are tanking with your back against a wall or stone or some sort of obstacle / you have a bryn equipped)
If you do get knocked back and your party attacks the MVP, it might very well turn to your party and wreak havoc.
When you do get knocked back, make sure to switch back to reflective gears and do your very best to catch its attention again instead of it turning towards your party (best would be that your party stopped attacking when it lost its attention on you), then switch back to reduction gears when that is done.
Take note that this applies to most higher level mobs as well, that switch targets easily when attacked. A prime example would be biolab monsters.
Hence a Sura tanking in TI using a reflective gear is also recommended to keep the party safer and also ease the work load of the party's healers (unless of course if the monsters are easily one-shotted then its quite safe to not use reflective gears to say the least)
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Get those Glorious Rings! or KBC carded accessory like you said yourself, they are probably the best all round accessory you can get.
There is the option of using RoR, mainly for self-assump, the heal might come in handy but always remember to switch it out when you have to recast MS.
Personally i find the RoR casts more of an annoyance and i won't touch it (personal preference).
There's a Perfect Dodge option of using Yoyo carded accessories in which case you'd probably optimize your tanking gears with P. Dodge, i never tried it myself so i cannot give any feedback on this.
You could try alligator carded accessories for reduction in long ranged skills like Clashing Spiral.
You can slot some of these cards in like a Cat Hand Glove, it gives some bonus stats.
Or maybe Waterdrop Brooches for abit of Max HP and MDef boost and water resist.
You can also use RWC pendants or rings which can give you some bonus stats or HP etc. depending on your enchants.
So of course, Cat Hand Gloves are the cheap alternatives while you work your way towards a more "end-game" accessory like a well enchanted RWC pendant or ring as you are very likely to be using them on your other characters as well. So if you get a KBC, i'd say slot in it in a RWC accessory as it'd be more "useful" for most of your characters with the enchants it provides, particularly spell enchants on the RWC pendant.
While you work towards that, get that glorious ring, KBC is not cheap and the zeny can be better spent elsewhere before getting a KBC.