Two similar party effects are not necessarily additive. Taiwan skill descriptions explicitly identify several pairs that do not apply together, and one pair has a higher-level rule with a named winner at equal levels. Check the particular effect before counting a second skill as extra damage, protection or target weakening.
The names below match the Traditional Chinese skill pages in the Taiwan explorer. This is a guide to those stated interactions, not a complete ranking of classes or a simulation of every buff in the game.
Cleric and 
Chanter buff priority
Cleric's 
保護之光 and Chanter's 
不敗真言 both provide party PvE/PvP damage amplification and damage tolerance. Their descriptions say that the effects cannot be used together: only the higher-level skill effect applies. At equal levels, only the Chanter's 不敗真言 applies.
For a party containing both classes, compare the actual skill levels rather than adding the displayed benefits together. Do not assume a lower-level second buff improves the first one. Conversely, this rule alone does not decide which character should bring other utility, healing or damage skills; it resolves this specific overlap.
The selected party buff names higher-level priority and the equal-level winner.
Chanter and Cleric target weakening
Chanter's passive 
大地約定 lowers the target's PvE/PvP damage tolerance after attacks. Its description says that, when Cleric's 
苦痛連鎖 is also applied, the tolerance-reduction effect from 大地約定 does not apply.
This is a stated priority, not a higher-level comparison. Do not transfer the tie rule from the previous pair to this one. It also does not mean that the Cleric's damage-over-time attack and the Chanter's entire kit are duplicates. The restriction names the target's tolerance reduction.
The target-tolerance reduction has a named priority, rather than a level comparison.
Gladiator and 
Templar party bonuses
Gladiator's passive 
老練反擊 increases the user's frontal damage amplification and, after a successful block, provides party PvE/PvP damage amplification. The description specifically says that the party amplification effects do not apply together with Templar's 
激昂.
The restriction does not name the separate frontal bonus as a duplicate. It also does not state a higher-level or equal-level winner for this pair. Count the party effects as non-stacking, but do not invent a priority rule or discard the rest of the passive's description.
The frontal self benefit and block-triggered party amplification are separate effects.
Gladiator and Templar attack reduction
Gladiator's 
激怒爆炸 applies a weakening effect that reduces the target's attack. That particular effect does not stack with the weakening effect from Templar's 
挑釁.
The Gladiator skill has other described behavior, including a self benefit and activation of another attack. “These weakening effects do not stack” is not the same as “these skills cannot both deal damage” or “one skill has no remaining use.” Read the restriction at the effect level, then inspect the other lines before changing a setup.
The weakening-effect restriction does not remove the skill’s other effects.
The shared protection lockout
Gladiator's 
毅力 lists a non-repeatable invulnerability condition: while that effect is present, the listed effects of 毅力, Cleric's 
救援, and Chanter's 
結界咒語 do not apply for 30 seconds. That is a timing restriction, not a reason to add their durations together into one uninterrupted protection window.
The same description warns that some powerful attacks are not blocked. Do not turn this into a universal immunity promise or extend the restriction to every defensive skill. A plan for a dangerous mechanic still needs the actual target, timing and the exact protection being used.
The protection description names the shared 30-second restriction and powerful-attack exception.
Choose complementary party effects
Before changing skills, identify the pair, the affected benefit and any stated priority or duration. Compare actual levels only when the rule says levels decide the result. A rule that does not specify a winner should not gain one because another pair uses that system.
Share the relevant skill page with the teammate bringing the overlapping effect. The skill-planning guide explains how to separate these party interactions from mastery upgrades, stigma slots and activation conditions. This keeps a narrow non-stacking rule from becoming an unsupported recommendation to replace an entire class or build.